Download NATIONAL HIGH SCHOOL CHEMISTRY EXAMINATION (1995

NATIONAL HIGH SCHOOL CHEMISTRY EXAMINATION (1995)
PART ONE – MULTIPLE CHOICE
1.
Mercury(I) compounds contain a diatomic cation whose formula is Hg2 2+. The total number of
electrons in this ion is
a) 156
2.
b) 158
d) 160
e) 162
Elements X and Y can combine to form two different compounds. If 1.60 g of X reacts with exactly
1.60 g of Y, the compound produced has the formula XY2 . However, under different conditions, 2.40
g of X will react with 1.60 g of Y to form a second compound, whose empirical formula is
a) X 3 Y 4
3.
c) 159
b) XY
c) XY 3
d) X 2 Y
e) X 4 Y 3
Benzene (C6 H 6 ) can react with fluorine according to the unbalanced chemical equation
C6 H 6 + F2 → C6 F 12 + HF
If this equation is balanced, the number of moles of F2 required to react with each mole of C6 H 6 is
a) 18
4.
b) 12
c) 9
d) 6
e) 3
Given the balanced equation
3 Cu(s) + 8 HNO3 (aq) → 3 Cu(NO3 ) 2 (aq) + 2 NO(g) + 4 H 2 O(l)
determine the mass of copper that would produce 0.167 mol NO(g) when reacted with excess nitric
acid.
a) 10.6 g
5.
d) 5.01 g
e) 15.9 g
b) C5 H 3
c) C2 H 5
d) C3 H 7
e) CH
d) the K atom
e) the Ca atom
Which one of the following has the largest radius?
a) the Na atom
7.
c) 190.6 g
A 1.56 g sample of a compound containing only carbon and hydrogen was completely burned. The
reaction produced 5.28 g of CO2 and 1.08 g of H2 O. What is the empirical formula of the
compound?
a) CH 2
6.
b) 31.8 g
b) the Mg atom
c) the Ca2+ ion
In which one of the following lists are all the substances covalently bonded?
a) NO, HBr, LiOH
b) CO2 , NH 3 , F 2
d) CH 4 , H 2 O, Ne
e) NaF, CCl 4 , Al(OH) 3
c) CO, BaCl2 , N 2
8.
At room temperature fluorine is a gas (boiling point –188°C), while bromine is a liquid (boiling
point +59°C). The difference in the physical states of these two halogens occurs because
a) the intermolecular forces in bromine are weaker
b) the covalent bonds in bromine are stronger
c) the intermolecular forces in bromine are stronger
d) the covalent bonds in bromine are weaker
e) the covalent bonds in bromine are more polar
9.
Which of the following statements about ionic compounds is FALSE?
a) Ionic bonding is due top electrostatic attraction
b) Every ion is charged
c) The formation of a binary ionic compound from its elements is exothermic
d) Every ion contains only one nucleus and a number of electrons which is different from the nuclear
charge
e) Ionic compounds which dissolve in water form conducting solutions
10. The following thermochemical equations apply to the reactions of iron with dioxygen:
Fe(s) + 1/2 O2 (g) → FeO(s) +133.2 kJ
2 Fe(s) + 3/2 O2 (g) → Fe2 O3 (s) + 738.1 kJ
How much heat is evolved in the reaction: 2 FeO(s) + 1/2 O2 (g) → Fe2 O3 (s) ?
a) 1004.5 kJ
b) 871.3 kJ
c) 471.7 kJ
d) 604.9 kJ
e) 1343.0 kJ
11. By photosynthesis using solar energy, maple trees make molecules of glucose in the reaction
6 CO2 (g) + 6 H2 O(l) → C6 H 12 O6 (s) + 6 O2 (g)
∆H = +2815 kJ/mol glucose
To make 20 g of glucose, how much solar energy must the maple leaves absorb (if the process is 100%
efficient)?
a) 239 kJ
b) 469 kJ
c) 141 kJ
d) 313 kJ
e) 15.6 kJ
12. A student generates 41.0 mL of dihydrogen (H2 ) by reacting solid magnesium with hydrochloric
acid at 20°C. He then heats the gas produced to 35°C without changing the pressure. What will
be the final volume of H2 ?
a) 43.1 mL
b) 71.8 mL
c) 39.0 mL
d) 23.4 mL
e) 80.5 mL
13. At 70°C and atmospheric pressure of 101.3 kPa, a light bulb with a volume of 212 mL contains 0.152 g
of a pure gas. What is this gas?
a) Ne
b) Ar
c) Kr
d) N 2
e) O 2
14. Two containers are filled with gas at the same temperature, one with H2 and the other with CO2 .
Which one of the following statements is consistent with the kinetic theory of gases?
a) The molecules of the two gases have the same average speed.
b) The molecules of the two gases have the same average kinetic energy.
c) All the molecules of the two gases have the same kinetic energy.
d) All of the molecules of the two gases have the same speed.
e) None of the above.
15. An aqueous solution of concentrated hydrobromic acid contains 48% HBr by mass. If the density of
the solution is 1.50 g/mL, what is its concentration?
a) 11.4 mol/L
b) 8.9 mol/L
c) 5.9 mol/L
d) 18.5 mol/L
e) 40.0 mol/L
16. In a certain solution the concentration of the OH– ion is 100 times greater than the concentration of
the H + ion. What is the pH of this solution?
a) 8b) 12
c) 6
d) 2
e) 14
17. Chlorine is a pale yellow-green gas, which, when dissolved in water, produces an aqueous solution
that
a) has a pH more acidic than 7, and has no redox properties.
b) has a pH more basic than 7 and is an oxidizing agent.
c) is neutral and is a reducing agent.
d) has a pH more acidic than 7 and is an oxidizing agent.
e) has a pH more acidic than 7 and is a reducing agent.
18. Formic acid (HCO2 H) is a weak monoprotic acid in aqueous solution.
An aqueous solution is made by dissolving 1.00 mol of formic acid in sufficient water to make 1.00 L
of solution. Which one of the following species is present in largest concentration?
a) H 3 O+
b) OH –
c) HCO 2 –
d) HCO 2 H
e) insufficient information is given to decide
19. Pure solid ammonium carbamate (NH4 CO2 NH 2 ) is put into a vessel which already contained
ammonia at a partial pressure of 10.1 kPa. The solid ammonium carbamate is allowed to dissociate
according to the equation:
NH 4 CO2 NH 2 (s) → 2 NH 3 (g) + CO2 (g)
The total pressure of the gases in equilibrium with the solid is 14.4 kPa. Calculate the value of the
equilibrium constant K p.
a) 1503 kPa2
b) 16.5 kPa2
c) 43 kPa 2
d) 241 kPa 2
e) 14.6 kPa2
20. Consider the equilibrium in the gaseous state
N 2 (g) + O2 (g) → 2 NO(g)
∆H = +180.5 kJ
Which of the following changes will displace the equilibrium and increase the number of moles of
NO present?
a) reduce the temperature
b) increase the pressure by reducing the volume
c) add oxygen
d) add a catalyst
e) remove nitrogen
21. A chemist finds the following values for the initial rate of the reaction
2 A(g) + B(g) → C(g)
Concentration [A} (mol/L)
0.50
1.0
1.0
1.5
1.0
Concentration [B] (mol/L)
0.50
0.50
1.0
1.0
1.5
Initial rate (mol/h)
0.020
0.080
0.080
0.18
0.080
The rate law expression for this reaction is
a) rate = k [A] [B]
b) rate = k [A]2 [B]
d) rate = k [A] 2
e) rate = k [B]2
c) rate = k [A]2 [B]2
22. What is the oxidation state of manganese in KMnO4 ?
a) +1
b) +5
c) +7
d) +2
e) +6
23. In the electrolysis of molten sodium chloride the reduction reaction is
a) Na → Na + + e–
b) Na+ + e– → Na
c) 2 Cl– → Cl 2 + 2 e–
d) 2 H+ + 2 e– → H2
e) Cl2 + 2 e– → 2 Cl–
24. A student mixed aqueous solutions of the following ionic compounds, and made the observations
listed in the table:
Solution A
Solution B
Observations
Ba(ClO 3 ) 2
Mg(IO 3 ) 2
a white precipitate formed
Mg(IO 3 ) 2
Pb(ClO3 ) 2
a white precipitate formed
MgCrO4
Pb(ClO3 ) 2
a yellow precipitate formed
MgCrO4
Ca(ClO 3 ) 2
no observable reaction
From these data, she can conclude that
a) both Ba(IO 3 ) 2 and Mg(ClO3 ) 2 are insoluble in water.
b) both PbCrO4 and Mg(ClO3 ) 2 are insoluble in water.
c) Ba(IO 3 ) 2 , Pb(IO 3 ) 2 , and PbCrO4 are insoluble in water.
d) all of Ba(IO 3 ) 2 , Mg(ClO 3 ) 2 , Pb(IO 3 ) 2 , PbCrO4 , and CaCrO 4 are insoluble in water.
e) only Ba(IO3 ) 2 and PbCrO4 are insoluble in water.
25. The solubility product constant of BiI3 is 8.2 x 10–19 . The solubility of this salt in pure water is
therefore
a) 9.1 x 10 –10 mol/Lb) 3.0 x 10–5 mol/L
c) 2.1 x 10–19 mol/L d) 5.9 x 10–7 mol/L
e) 1.3 x 10–5 mol/L
NATIONAL HIGH SCHOOL CHEMISTRY EXAMINATION (1995)
PART TWO - ESSAY QUESTIONS
Discuss THREE of the following five topics in essay form. These are to be scientific essays and
therefore equations, formulas ,diagrams, etc., are highly appropriate. A clear, concise and wellorganized essay will be rated higher than a long rambling one which contains the same information.
1.
this year is the 100th anniversary of the discovery of X-rays and next year will be the 100th
anniversary of radioactivity. Today the words "radiation" and "radioactivity" may bring to mind
both positive and negative reactions. Describe the main forms of ionizing radiation, and explain
the positive and negative effects of their use on our quality of life.
2.
Acids and bases are two very important classes of substances, but several different definitions of
these terms are used by chemists. Explain the various definitions of acids and bases, and give
examples of substances which are acidic and basic according to each definition.
3.
Describe an experiment which would allow you to measure the heat (or enthalpy change) of a
chemical reaction. Suggest a specific reaction and describe the apparatus which you would use and
the procedure which you would follow. What type of results would you expect and how would you
interpret the data?
4.
About 90% of the chemical substances which have been discovered are compounds of carbon, also
known as organic compounds. Describe the structures and properties of some classes of organic
compounds,as well as their importance in our lives.
5.
What is a catalyst? Describe some commonly used types of catalyst, and indicate the types of
reactions which they can catalyse.
NATIONAL HIGH SCHOOL CHEMISTRY EXAMINATION (1996)
PART ONE – MULTIPLE CHOICE
1.
The ion which has 35 protons, 44 neutrons and 36 electrons is:
A. 79 K +
2.
D. 80 Br –
E. 79 Br –
B. K 2 O3
C. CrO3
D. Al 2 O3
E. VO 3
Ammonia (NH 3 ) reacts with fluorine (F2 ) to form dinitrogen tetrafluoride (N2 F 4 ) and HF.
In this reaction, how much fluorine can react with 17.0 g of ammonia?
A. 119 g
4.
C. 80 Kr +
An element X forms two oxides whose formulas are XO3 and X2 O3 . One of these oxides
contains 52% of X by mass and has a molar mass of 99.98. What is the formula of this
oxide?
A. Mg2 O3
3.
B. 79 Br +
B. 95.0 g
C. 38.0 g
D. 190 g
E. 47.5 g
Platinum is a useful and relatively inert metal, but it will dissolve in aqua regia, a mixture
of nitric and hydrochloric acids.
The reaction is 3 Pt(s) + 4 HNO3 (aq) + 18 HCl(aq) → 3 H2 PtCl 6 (aq) + 4 NO(g) + 8 H 2 O(l)
How many grams of nitric oxide (NO) are formed when 11.6 g of Pt dissolves?
A. 14.98 g
5.
E. 7.13 g
B. 312 mL
C. 2.79 mL
D. 3.72 mL
E. 4.95 mL
B. K +
C. F –
D. Cl–
E. O2–
The radioactive isotope Na-24 is used to observe the circulation of blood. What isotope is
produced when Na-24 decays by emitting a beta particle, which is a fast-moving electron?
A. Mg-24
8.
D. 2.38 g
Which of the following ions has the largest radius?
A. S 2–
7.
C. 1.34 g
The aqua regia can be prepared with concentrated nitric acid whose concentration is 16M (16
mol/L). What volume of this acid would be required for complete reaction with 11.6 g of
Pt?
A. 35.5 mL
6.
B. 1.78 g
B. Na-25
C. Ne-23
D. Na-23
E. Mg-25
Oxygen condenses at –183°C and freezes at –223°C. According to the kinetic molecular
theory, the kinetic energy of oxygen molecules is zero at
A. –183°C
B. –273°C
C. –373°C
D. –223°C
E. 0°C
9.
Benzoic acid, C7 H 6 O2 , is found in certain berries. A sample of 1.425 g of benzoic acid is
burned in a combustion calorimeter, and the temperature increases from 23.60°C to 32.33°C.
The calorimeter has a heat capacity of 893 J K–1 , and it contains 775 g of water whose
specific heat is 4.184 J K–1 g–1 . How much heat is released by the combustion of the
sample?
A. 14.6 kJ
B. 51.4 kJ
C. 25.3 kJ
D. 36.1 kJ
E. 28.3 kJ
10. Find the enthalpy change (∆H) for the reaction: C2 H 4 (g) + 6 F2 (g) → 2 CF4 (g) + 4 HF(g)
using the following thermochemical data:
C(s) + 2 F2 (g) → CF4 (g)
∆H = –680 kJ
2 C(s) + 2 H2 (g) → C2 H 4 (g)
∆H = +52 kJ
H 2 (g) + F2 (g) → 2 HF(g)
∆H = –537 kJ
A. –2382 kJ
B. –3560 kJ
C. –1269 kJ
D. –2486 kJ
E. –1165 kJ
11. An automobile cylinder has a volume of 450 cc. The engine takes in air at a pressure of 1.00
atm and a temperature of 27°C, and compresses it to a volume of 50.0 cc at 77°C. What is
the final pressure of air in the cylinder?
A. 1.17 atm
B. 7.7 atm
C. 9.0 atm
D. 25.7 atm
E. 1.66 atm
12. Nickel tetracarbonyl, Ni(CO) 4 , is formed by the reaction of nickel metal and carbon
monoxide. If 0.118 g of nickel reacts at 21°C with 570 mL of CO at an initial pressure of 2.00
atm, what is the pressure of CO after the reaction?
A. 0.34 atm
B. 0.64 atm
C. 1.92 atm
D. 0.085 atm
E. 1.66 atm
13. Which substance would you expect to have the highest melting point.
A. GeI 4
B. I 2
C. KI
D. CH 3 I
E. HI
14. Solid CO2 is called "dry ice", because it changes directly from a solid to a gas at –78°C
without ever becoming liquid (at 1 atm pressure). When solid CO2 becomes a gas:
A. Its energy decreases and its entropy decreases
B. Its energy is constant and its entropy increases
C. Its energy decreases and its entropy increases
D. Its energy increases and its entropy increases
E. Its energy increases and its entropy decreases
15. If the intermolecular forces in liquid A are stronger than in liquid B, then compared to
liquid A:
A. Liquid B has a lower boiling point and a lower vapor pressure at 25°C
B. Liquid B has a lower boiling point and a higher vapor pressure at 25°
C. Liquid B has a higher boiling point and a lower vapor pressure at 25°C
D. Liquid B has a higher boiling point and the same vapor pressure at 25°C
E. Liquid B has a higher boiling point and a higher vapor pressure at 25°C
16. An antifreeze mixture consists of 40% ethylene glycol (C2 H 6 O2 ) by weight in aqueous
solution. If the density of this solution is 1.05 g/mL, what is the molar concentration?
A. 6.77 M
B. 6.45 M
C. 0.017 M
D. 16.9 M
E. 7.11 M
17. The decomposition reaction PCl 5 (g) → PCl 3 (g) + Cl 2 (g) has an equilibrium constant of
0.245 at 300°C. What happens in a container which contains the three gases each at a
concentration of 0.30 mol/L?
A. The concentration of PCl 5 increases and those of PCl 3 and Cl2 decrease
B. The concentrations of Cl2 and PCl5 increase and that of PCl3 decreases
C. The concentration of PCl 3 and Cl2 increase and that of PCl5 decreases
D. The concentration of PCl 3 and PCl5 increase and that of Cl2 decreases
E. The mixture remains in a state of equilibrium
18. How would you increase the yield of products at equilibrium in the reaction
SO 2 (g) + NO 2 (g) → SO 3 (g) + NO(g)
∆H = –42 kJ
Assume that all the gases behave ideally.
A. Add a catalyst
B. Decrease the volume
C. Increase the volume
D. Decrease the temperature
E. Increase the temperature
19. The common automobile battery contains
A. carbonic acid (H2 CO3 )
B. sulphuric acid (H2 SO 4 )
D. acetic acid (C2 H 4 O2 )
E. nitric acid (HNO3 )
C. hydrochloric acid (HCl)
20. The ion H 2 PO4 – can act as either an acid or a base. Its conjugate base and acid are
respectively
A. H 3 PO4 and HPO4 2–
B. HPO4 2– and H3 PO4
D. H 3 PO4 and PO4 3–
E. PO4 3– and H3 PO4
C. PO4 3– and HPO4 2–
21. What is the pH of a solution of 10–9 M NaOH?
A. 9
B. 7
C. 6
D. 5
E. 8
22. A 0.01 M solution of a of a certain weak acid (HA) has a pH of 5.0. What is the ionization
constant (K a ) of this acid?
A. 1.0 x 10–12
B. 1.0 x 10–5
C. 1.0 x 10–7
D. 1.0 x 10–8
E. 1.0 x 10–3
23. The solubility of AgBr in pure water is 5.7 x 10–7 M (at 25°C). What is the solubility of
AgBr in a solution which contains 0.01 mol of NaBr per litre?
A. 3.25 x 10–13 M
B. 5.7 x 10–5 M
C. 7.55 x 10–5 M
D. 5.7 x 10–7 M
E. 3.25 x 10–11 M
24. The reaction CO(g) + NO2 (g) → CO2 (g) + NO(g) is second order in NO2 and zero order in
CO. If the concentration of CO is doubled and that of NO2 is halved, the reaction rate will
be:
A. halved
B. divided by 4
C. multiplied by 4 D. unchanged
E. doubled
25. The reduction potentials of silver and nickel are E(Ag+,Ag) = +0.80 V and E(Ni2+,Ni) = –
0.25 V. Which of the following statements is true?
A. Ag+ is an oxidizing agent but Ni 2+ is a reducing agent
B. Ag + is a better oxidizing agent than Ni2+ and Ag is a better reducing agent than Ni
C. Ni 2+ can be reduced by silver metal
D. Ag+ is a better oxidizing agent than Ni2+ and Ni is a better reducing agent than Ag
E. Ni 2+ is a better oxidizing agent than Ag+ and Ag is a better reducing agent than Ni
NATIONAL HIGH SCHOOL CHEMISTRY EXAMINATION (1996)
PART TWO - ESSAY QUESTIONS (Choose 3)
Answer THREE questions only in the form of scientific essays including any appropriate
equations, formulas and diagrams. The judging of the essays will be based on both factual
accuracy and presentation. A clear, concise and well-organized essay will be rated higher than
a long rambling one which contains the same information.
1.
The 1995 Nobel Prize in Chemistry was awarded to three scientists who discovered
possible danger to the earth's ozone layer. Discuss the problem of the ozone layer: where is
it found, how is it formed, why is it important, and what is the nature of the danger?
2.
Describe the properties and importance of three of the six alkaline earth metals. (Be, Mg,
Ca, Sr, Ba, Ra)
3.
Explain the different types of bonds between atoms, both strong and weak. How is each
type of bond formed? In what substances is each type of bond found? What are their
relative strengths?
4.
Chemical analysis (or analytical chemistry) deals with methods of determining the
compositions of mixtures. Explain some methods for determining the concentration of a
substance ion a mixture.
5.
What is an oxidation-reduction reaction? Give a variety of examples both with and
without the breaking of chemical bonds. Give some examples of oxidation-reduction
reactions which are useful and explain their use.
1997 NATIONAL CHEMISTRY EXAMINATION
CIC National High School Chemistry Examination
CCO National Selection Examination
PART A: MULTIPLE CHOICE QUESTIONS (60 minutes)
1. The fundamental basis of the present-day periodic table is that the elements are
A. arranged in order of increasing atomic weight.
B. taken in groups of eight.
C. arranged in order of increasing number of protons in the atomic nucleus.
D. grouped according to chemical properties.
E. arranged in order of increasing number of neutrons in the atomic nucleus.
2. A certain gas is an oxide of nitrogen containing 30.51% N by mass, with a density of 4.085 g/L
at 0°C and 101.3 kPa. The formula of this gas is
A. N 2 O4
B. NO2
C. NO
D. N 2 O
E. N 2 O5
3. Magnesium oxide and phosphorus pentachloride gas react to form magnesium chloride and
diphosphorus pentoxide. If MgO is present in excess, what mass of PCl5 is needed to form 284
g of P2 O5 ?
A. 249 g
B. 417 g
C. 833 g
D. 403 g
E. 208 g
4. You have a solution which is 0.350 mol/L in CaCl2 . What volume of this solution would you
require in order to dispense 0.070 moles of chloride ion?
A. 50 mL
B. 100 mL
C. 200 mL
D. 400 mL
E. 1000 mL
5. If AgBr is assumed to be completely insoluble, what mass of AgBr precipitates when 30.0 mL
of an 0.500 mol/L solution of AgNO3 is added to 50.0 mL of an 0.400 mol/L solution of NaBr?
A. 3.76 g
B. 1.28 g
C. 6.57 g
D. 3.76 kg
E. 2.82 g
6. Aspirin can be prepared from salicylic acid (C7 H 6 O3 ) and acetic anhydride (C4 H 6 O3 )
according to the equation
2 C7 H 6 O3 + C4 H 6 O3 → 2 C9 H 8 O4 + H2 O
This reaction gives a yield of 74%, provided that a 50% excess of acetic anhydride (the
cheaper reagent) is used. If a chemist wants to prepare 20.0 g of aspirin in the laboratory,
what mass of acetic anhydride should she use?
A. 20.7 g
B. 11.5 g
C. 23.0 g
D. 7.65 g
E. 8.50 g
7. A chemist synthesizes a new acidic compound which has two acidic hydrogen atoms per
molecule. He dissolves a sample of 1.26 g of the pure compound in water and titrates with
0.100 mol/L NaOH. If 75.0 mL of NaOH are required to reach the end point, what is the
molar mass of the new acid?
A. 336 g/mol
B. 168 g/mol
C. 80 g/mol
D. 1344 g/mol
E. 672 g/mol
8. Which of the following elements has the largest density at 25°C and atmospheric pressure
(101.3 kPa)?
A. Li
B. Cs
C. Al
D. Pb
E. Rn
9. Radioactive isotopes such as 137 Cs can be formed in nuclear reactors when a nucleus of 235 U
absorbs a neutron and undergoes fission into two other nuclei, while emitting more neutrons.
In a given fission event, the products are 137 Cs and an isotope of rubidium, while three
neutrons are emitted in the fission. Which isotope of rubidium is formed?
A. 96 Rb
B. 98 Rb
C. 85 Rb
D. 87 Rb
E. 95 Rb
10. A double bond between two carbon atoms is formed when:
A. one electron is shared
B. two electrons are shared
C. four electrons are shared
D. one electron is transferred
E. two electrons are transferred
11. Which of the following molecules forms no intermolecular hydrogen bonds?
A. CH 3 CH 2 OH
B. HF
C. H2 O
D. CH 3 COOH
E. H2
12. Acetylene (HC≡CH) can add two molecules of hydrogen according to the equation
C2 H 2 + 2 H2 → C2 H 6 . Find the heat released (in kJ/mol) during this reaction, using the
required bond energies from the following list:
C-H 413
A. 1160
C-C 347
C=C 614
C≡C 839
H-H 432
B. 521
C. 563
D. 296
E. 788
13. A rigid balloon with a volume of 50.0 cm3 is kept at 18°C and contains air at a pressure of
101.3 kPa initially. If 0.223 g of krypton is now introduced, what will be the pressure of
krypton inside the balloon?
A. 128.8 kPa
B. 64.4 kPa
C. 27.5 kPa
D. 230.1 kPa
E. 7.97 kPa
14. Air is a mixture whose principal components are N2 and O2 . According to the kineticmolecular theory of gases, at what temperature is the average speed of N2 molecules equal
to the average speed of O2 molecules at 0°C?
A. +39°C
B. +84°C
C. +19°C
D. -18°C
E. -34°C
15. Which of the following formulas could NOT be that of an alcohol?
A. CH 4 O
B. C2 H 6 O2
C. C2 H 7 NO
D. C2 H 7 N
E. C2 H 4 O3
16. Commercial chemical suppliers sell perchloric acid (HClO4 ) as a 70.0% solution (by mass)
in water. If the density of this reagent is 1.664 g/mL, what is the molar concentration of
HClO 4 in the solution?
A. 6.97 mol/L
B. 16.6 mol/L
C. 4.97 mol/L
D. 23.2 mol/L
E. 11.6 mol/L
17. The gas NO2 reacts to form a dimer N2 O4 according to the equation
2 NO 2 (g) → N2 O4 (g); ∆H = -57.2 kJ
There will be more N2 O4 present at equilibrium if:
A. the temperature is increased or the volume is increased
B. the temperature is increased or the volume is decreased
C. the temperature is decreased or the volume is increased
D. the temperature is decreased or the volume is decreased
E. the temperature is increased, while a change in volume has no effect
18. In a properly functioning automobile engine, the two principal products of the combustion of
the gasoline are:
A. CO and H2 O
B. CO 2 and H2 O
D. CO and NO
E. CO2 and NO
C. H2 O and NO
19. Which oxide is the principal component of glass?
A. TiO 2
B. Al2 O3
C. K2 O
D. Fe 2 O3
E. SiO 2
20. If two mol of lithium hydroxide are neutralized by one mol of an acid in aqueous solution,
then
A. the acid is twice as concentrated as the lithium hydroxide solution.
B. the lithium hydroxide solution is twice as concentrated as the acid.
C. two mol of acid supply one mol of hydrogen ions.
D. one mol of acid supplies two mol of hydrogen ions.
E. one mol of acid supplies one mol of hydrogen ions.
21. The ion H 3 O+ is an acid according to the Brønsted-Lowry definition. What is the conjugate
base of this acid?
A. another H3 O+
B. H+
C. H2 O
D. OH –
E. H3 O+ has no conjugate base
22. A 0.1 mol/L solution of potassium acetate, KC 2 H 3 O2 , has a lower pH than a 0.1 mol/L
solution of potassium cyanide, KCN. From this, you can correctly conclude that
A. hydrocyanic acid, HCN, is a weaker acid than acetic acid, HC2 H 3 O2 .
B. hydrocyanic acid, HCN, is less soluble in water than acetic acid, HC2 H 3 O2 .
C. the cyanide ion, CN– , is a weaker base than the acetate ion, C2 H 3 O2 – .
D. cyanides are less soluble in water than acetates.
E. acetate ion, C2 H 3 O2 , partially dissociates to form hydronium ion, H3 O+.
23. The catalyst in a chemical reaction:
A. decreases the activation energy of the forward reaction and increases the activation
energy of the reverse reaction
B. increases the activation energy of the forward reaction and decreases the activation
energy of the reverse reaction
C. increases the activation energies of both the forward reaction and the reverse reaction
D. decreases the activation energies of both the forward reaction and the reverse reaction
E. increases the activation energy of the forward reaction and does not change the
activation energy of the reverse reaction
24. Hydrazine is a liquid of formula N2 H 4 which has been used as a rocket fuel. What is the
oxidation number of N in hydrazine?
A. +5
B. -3
C. +2
D. 0
E. -2
25. A metal M displaces copper from an aqueous solution of copper(II) sulfate but does not react
with an aqueous solution of zinc nitrate. Which one of the following lists gives the metals in
order of increasing strength as a reducing agent?
A. Cu < Zn < M
B. Cu < M < Zn
D. M < Cu < Zn
E. Zn < Cu < M
C. Zn < M < Cu
NATIONAL HIGH SCHOOL CHEMISTRY EXAMINATION (1997)
PART B - ESSAY QUESTIONS (Choose 2)
Answer TWO questions only in the form of scientific essays including any appropriate
equations, formulas and diagrams. The judging of the essays will be based on both factual
accuracy and presentation. A clear, concise and well-organized essay will be rated higher than
a long rambling one which contains the same information.
1. Canadian mining has been in the news with the 1996 discovery of ore deposits in Labrador.
Select any three of aluminum, copper, iron, gold or nickel, which are all important in
Canadian mining. Discuss the natural form in which these three metals are found, and the
chemistry needed to bring them into the metallic form. Describe the corrosion of these
metals, and how they may be protected from corrosion or recycled.
2. The chemistry of life is called biochemistry, a field which combines both chemistry and
biology. Discuss some of the chemical substances found in living organisms? Describe their
role in biology.
3. Many chemists have studied solutions which conduct electricity. Why do solutions conduct
electricity and why do some conduct better than others? What chemical information can be
learned from measurements of electrical conductivity? Describe some useful applications of
conducting solutions in everyday life.
1998 NATIONAL CHEMISTRY EXAMINATION
CIC National High School Chemistry Examination
CCO National Selection Examination
PART A: MULTIPLE CHOICE QUESTIONS (60 minutes)
1.
Which one of the following isotopes has exactly 19 neutrons?
a) 35 Cl
2.
b) 19 F
b) 1.6 x 1023
c) 7.8 x 1022
d) 3.6 x 1022
e) 6.0 x 1023
b) Al3 NO 3
c) Al2 (NO 3 ) 3
d) Al(NO3 ) 2
e) Al(NO3 ) 3
An 0.5000 g sample of magnetite ore (impure Fe3 O4 ) is treated so that the iron is
precipitated as iron(III) hydroxide. The precipitate is heated and converted to 0.4980 g
Fe 2 O3 . What is the percent Fe3 O4 in the ore?
a) 69.0%
5.
e) 35 Ca +
The correct formula for aluminium nitrate is:
a) AlNO 3
4.
d) 39 K
The principal ingredient listed for chocolate bars is sugars, typically about 47% of milk
chocolate bars. If these sugars are represented by sucrose, C 12 H 22 O11 , how many sugar
molecules are in a 43 g chocolate bar?
a) 9.8 x 1026
3.
c) 35 S
b) 96.3%
c) 99.6%
d) 35.0%
e) 48.1%
Which one of the following tests specifically indicates the presence of an acid in an
aqueous solution?
a) Red litmus paper remains red when a drop of the solution is added.
b) Bubbles of gas are given off when the solution is added to a calcium carbonate solution.
c) The solution conducts electricity.
d) The solution is colourless.
e) The solution turns pink when phenolphthalein is added.
6. The antacid "Milk of Magnesia" is an aqueous slurry of magnesium hydroxide,
containing about 80 mg Mg(OH)2 per mL. What volume of gastric juice (stomach acid)
which is about 0.17 mol/L HCl can be neutralized by 1 tablespoon (15 mL) of "Milk of
Magnesia"?
a) 7.1 L
b) 0.00122 L
c) 0.0611 L
d) 0.122 L
e) 0.242 L
7.
A plastic bottle contains 0.60 g of nitrogen, N2 . Another bottle of the same size is filled at
the same temperature and pressure with an unknown gas. If the mass of the second gas is
1.52 g, this gas can be:
a) air
8.
b) Cl2
c) O2
d) CH4
e) CO2
A balloon probe is filled with 150 L of helium at ground level where the atmospheric
pressure is 102 kPa and the temperature is 30°C. The balloon bursts at an altitude where the
temperature is –5°C and the pressure 50 kPa. What is the volume of the balloon just before
it bursts?
a) 270 L
b) 346 L
c) 51 L
d) 65 L
e) 83 L
9.In which of the following substances is the bonding the most ionic?
a) H2
b) NaBr
c) Br2
d) Na
e) HBr
10. Which of the following substances has the lowest normal boiling point?
a) NH3
b) H2 O
c) HF
d) CH3 OH
e) CH4
11. The heats of formation of methane, CH4 , and propane, C3 H 8 , are given by the equations:
C(s) + 2 H2 (g) → CH4 (g)
∆H = -74.9 kJ
3 C(s) + 4 H2 (g) → C3 H 8 (g)
∆H = -103.8 kJ
What is the heat of reaction for the transformation of 3 mol methane into 1 mol propane:
3 CH4 (g) → C3 H 8 (g) + 2 H2 (g) ?
a) -178.7 kJ b) -328.5 kJ
c) +120.9 kJ
d) +28.9 kJ
e) -28.9 kJ
12. A solution containing 12.0% sodium hydroxide by mass has a density of 1.131 g/mL. What
volume of this solution contains 5.00 mol of NaOH?
a) 0.0240 L
13.
b) 1.67 L
c) 1.47 L
d) 1.00 L
e) 0.177 L
As the temperature of a solution increases:
a) the solubilities of most solids increase and those of gases do not vary
b) the solubilities of most solids decrease and those of gases decrease
c) the solubilities of most solids decrease and those of gases increase
d) the solubilities of most solids increase and those of gases decrease
e) the solubilities of most solids increase and those of gases increase
14. Which one of the following compounds is an alcohol?
H
a) CH3
CO
CH3
b) CH3
C
O
c) CH3
OH
d) CH4
e) CH3
COOH
15. Which one of the following classes of molecules, important in biology, contains nitrogen?
a) fatty acids
b) carbohydrates
c) proteins
d) sugars
e) fats
16. Which of the following metals is protected by an almost impenetrable surface oxide
coating?
a) Ag
b) Al
c) Au
d) Fe
e) Cu
17. The decomposition of nitrosyl chloride is described by the equation:
2 NOCl(g) → 2 NO(g) + Cl2 (g)
A round flask initially contains pure NOCl gas at 400 K and a pressure of 2.75 atm. When
equilibrium is reached, the total pressure equals 3.58 atm. What is the value of the
equilibrium constant KP?
a) 0.36 atm b) 0.16 atm c) 0.045 atm d) 1.93 atm e) 1.26 atm
18. The Mond process for the refining of nickel involves the exothermic reaction
Ni(s) + 4 CO(g) → Ni(CO)4 (g)
If this reaction is at equilibrium at 200°C, which one of the following operations does not
result in a net reaction?
a) addition of CO
b) addition of Ni(CO)4
d) reducing the volume
e) addition of Ni
c) heating to 250°C
19. Nitrous acid, HNO2 , is a weak monoprotic acid in aqueous solution whose acid
equilibrium constant Ka = 4.5 x 10–4 at 25°C. Its conjugate base is the nitrite ion, NO2 – , is
expected to be:
a) unreactive with acids
b) a strong base
c) a stronger base than hydroxide ion, OH–
d) a weak base
e) a weaker base than water
20. At 50°C the ion product of water has the value Kw = 5.5 x 10–14 mol2 L–2 . What is the pH
of a neutral aqueous solution at 50°C?
a) 7.00 b) 13.26 c) 2.3 x 10–7
d) 1.0 x 10–7
e) 6.63
21. In which one of the following molecules are the atoms not all in one plane?
a) CH4
b) C2 H 4
c) C6 H 6
d) H2 O
e) H2 CO
22. Codeine is a derivative of morphine used as an analgesic, formerly used in over-the-counter
cough syrups but now only available by prescription because it is addictive. Codeine is a
weak monoprotic base of formula C18 H 21 NO 3 and basicity constant Kb = 8.9 x 10–7 .
Estimate the pH of a solution containing 10.0 mg of codeine dissolved in 20.0 mL of water.
a) 10.24
b) 9.59
c) 7.95
d) 6.05
e) 4.41
23. Which one of the following statements about catalytic reactions is correct?
a) The activation energy of the catalytic reaction is smaller than that of the non-catalytic
reaction.
b) The activation energy of the catalytic reaction is larger than that of the non-catalytic
reaction.
c) Either the reactants or the products of the catalytic reaction are different than those of
the non-catalytic reaction.
d) The heat of reaction of the catalytic reaction is smaller than that of the non-catalytic
reaction.
e) The heat of reaction of the catalytic reaction is larger than that of the non-catalytic
reaction.
24. The mechanism for the thermal decomposition of ozone (with no catalyst) in an excess of
oxygen is believed to be:
O3
O + O3
O2 + O
2 O2
(fast equilibrium)
(slow)
What is the rate law according to this mechanism?
a) rate = k[O3 ]2 /[O2 ]
b) rate = k[O 2 ][O]/[O3 ]
d) rate = k[O 3 ]
e) rate = k[O3 ]2
c) rate = k[O 3 ]/[O2 ][O]
25. Which one of the following statements is correct for an electrochemical cell in which the
reaction 2 Al + 3 Co2+ → 2 Al 2+ + 3 Co takes place?
a) The mass of the cobalt electrode decreases
c) Al 3+(aq) is the oxidizing agent
d) Co2+(aq) + 2 e – → Co(s) represents the reduction reaction
e) Co2+(aq) is the reducing agent
b) Co(s) is the anode
NATIONAL HIGH SCHOOL CHEMISTRY EXAMINATION (1998)
PART B - ESSAY QUESTIONS (Choose 2)
Answer TWO questions only in the form of scientific essays including any appropriate
equations, formulas and diagrams. Each question is of equal value. The judging of the essays
will be based on both factual accuracy and presentation. A clear, concise and well-organized
essay will be rated higher than a long rambling one which contains the same information.
1.
The year 1997 saw major new developments in the petroleum industry off the east coast of
Canada. The first crude oil was pumped from the Hibernia oil field and development of the
Sable Island gas field was approved.
List and give structures for some important molecules found in crude oil and natural gas.
Describe the overall processes used to convert crude oil or natural gas into useful fuels, and
comment on the removal of unwanted impurities from the crude materials. Discuss the
chemistry of burning oil and gas, and the correct stoichiometry for efficient combustion.
Explain how carbon monoxide can be produced by incorrect combustion of hydrocarbon fuels,
and why nitrogen oxides are significant byproducts of diesel engines. Mention possible
environmental effects of these compounds.
2. Water is a liquid with many exceptional properties. Compare the properties of water with
those of other liquids. Explain these properties with reference to the structure of water
molecules and the forces between these molecules. Give examples of the importance of the
properties of water in chemistry and in biology.
3. In recent years, several new forms of elemental carbon have been discovered. Describe the
structures and compare the properties of the various forms of carbon, both old and new.
INTERNATIONAL CHEMISTRY OLYMPIAD and CHEMICAL INSTITUTE OF CANADA
Final Selection Examination 1998
PART C: Free Response Development Problems
60%
Time: 1.5 hours
This segment has six (6) questions. A normal requirement is that a student attempt only 4
questions for a complete examination in 1.5 hours. Each of the 4 questions you select is worth
15%.
Your answers are to be written on the paper provided by your test supervisor. Be sure to number
each question attempted clearly and place your name on the top of the page. This cover page is
to be stapled securely to your answers.
1.
Among the tests that are carried out to evaluate the air quality of polluted sites is the
determination of the concentration of carbon dioxide, CO2 , in air. This analysis involves
the passage of a given volume of air through lime-water [an aqueous suspension of
Ca(OH) 2 ], so that all the CO2 present is precipitated as calcium carbonate, CaCO3 .
a) A 10.0-L sample of polluted air at a temperature of 25.0oC and atmospheric pressure of
98.66 kPa was treated by this method and 0.0650 g of CaCO3 were obtained. Calculate
the percentage by volume of CO2 in the air sample.
The acidity of natural waters is influenced by gas absorption. On sites where the
quantities of nitrogen and sulfur oxides are negligible, the most important gas having an
effect on water acidity is carbon dioxide. It is the case for the polluted site mentioned
in (a).
b) From the data given in (a), and assuming that equilibrium has been reached between
gaseous and aqueous CO2 , calculate the pH of the water in a lake that is located on the
polluted site. Appropriate constants at 25oC are:
K H(CO 2 ) = 3.35 × 10–4 mol L–1 kPa –1
K b(HCO 3 – ) = 2.24 × 10–8 ,
K b(CO 3 2– ) = 2.14 × 10–4 .
(Henry’s Law constant for CO2 )
2.
a) Silver chloride, AgCl, is sparingly soluble in water; its solubility product constant, K sp,
has the value: K sp = 1.8 x 10–10 mol2 L–2 .
i)
Calculate the solubility of silver chloride in water.
ii) Would you expect the solubility of silver chloride in an aqueous solution of sodium
chloride, NaCl, to be larger or smaller than in water? Briefly explain your answer;
including chemical equations, if useful.
iii)Would you expect the solubility of silver chloride in an aqueous solution of
ammonia, NH3 (aq), to be larger or smaller than in water? Briefly explain your
answer; including chemical equations, if useful.
b) The standard molar (Gibbs) free energies of formation at 25°C are:
solid silver sulfate, Ag2 SO 4 (s)
∆Gof= –618.5 kJ mol–1
solid silver chloride, AgCl (s)
∆Gof = –109.8 kJ mol–1
aqueous chloride ion, Cl– (aq)
∆Gof = –132.3 kJ mol–1
aqueous sulfate ion, SO4 2– (aq)
∆Gof = –744.6 kJ mol–1
From the information in this question, determine the solubility product for silver
sulfate, Ag2 SO 4 , at 25°C.
3.
A 2.00-L flask contains a gas, A2 , at 0.100 kPa and 300 K. The reaction
A2 (g) + hν
→
2 A (g)
is performed photochemically with a UV radiation of 200 nm. Each molecule of A2 will
react after absorption of one photon.
a) Assuming that 1015 photons are absorbed per second, calculate the rate of the reaction.
b) Calculate the half-life of the reaction.
c)
Variation of the concentration of A with time can be followed via the UV-VIS
absorption of A at 400 nm in a gas cell with a path length of 10.0 cm. If the absorption is
of 0.182 after 3.00 hours, calculate the molar extinction coefficient (molar absorptivity)
of A.
4.
The molecular orbital energy-level diagram illustrated below may be used for dioxygen and
difluorine, but not the other diatomic molecules (B2 , C2 , N 2 ) in this same row of the
periodic table. In fact, for B2 , C2 , N 2 , the 2p atomic orbitals give rise to π bonding
molecular orbitals which are of lower energy than the σ bonding molecular orbital.
σ∗
h
f
π∗
j
2p
2p
e
Energy
i
g
2s
d
c
1s
b
a
O
O2
π
σ
σ∗
2s
σ
σ∗
1s
σ
O
a) Write the ground-state electron configuration for an oxygen atom.
b) Write the ground-state electron configuration for a dioxygen molecule.
c)
Why do orbitals labelled as “e” and “i” have the same energy?
d) Use the molecular orbital energy-level diagram to determine the bond order of
dioxygen and difluorine.
e) State if dioxygen and difluorine are diamagnetic or paramagnetic molecules.
f)
How does the fact that B2 is paramagnetic prove that the molecular orbital energylevel diagram for dioxygen is not correct for the B2 diatomic species?
g) Using these energy level diagrams, what is the bond order for each of the diatomic CN,
NN, and NO molecules?
h) Which of CN, N 2 , and NO has the highest IE (ionization energy)? Which has the
lowest IE?
[IE(X) = ∆H of(X +) – ∆H of(X)]
5.
a) Draw a structure for the organic compound 2-chloro-3-methylhex-3-ene.
b) Indicate the hybridization of carbon 2 and carbon 3.
c)
Give the approximate bond angles at carbon 2 and carbon 3.
d) Give the total number of carbon-carbon sigma (σ) bonds in the molecule.
e) Give the total number of pi (π) bonds in the molecule.
f)
How many asymmetric centres are there in the molecule?
g) How many stereoisomers exist for this molecule?
h) Draw a three dimensional representation of each of the stereoisomers and indicate the
appropriate stereochemistry using the labels R, S, E, and Z.
6.
Give the structures of the compounds B, C, D, E, F, G, and H involved in the reactions below.
E
HCl
Mg in ether
acetone
C2H5Br
B
H2O
C
HCl
ZnCl2
D NaOH
heat
HBr
CH3 -C=CH-CH3
H2 O2
CH3
O3
Zn,H2 O
G + H
(End of Part C Examination)
F
1999 NATIONAL CHEMISTRY EXAMINATION
CIC National High School Chemistry Examination
CCO National Selection Examination
PART A: MULTIPLE CHOICE QUESTIONS (60 minutes)
1. Which two atoms have the same number of neutrons?
a) 24Na and 24Mg
b) 14C and 14N
c) 23Na and 24Mg
12
14
12
14
d) C and C
e) C and N
2. The element rubidium (Rb) has two naturally occurring isotopes of mass 84.91 and 86.91. The natural abundance of the
lighter isotope ( 85Rb) is:
a) 23.5%
b) 76.5%
c) 50%
d) 28%
e) 72%
3. What is the oxidation state of chromium in the chromate ion (CrO42-)?
a) +8
b) +6
c) +4
d) +2
e) 0
4. The explosive trinitrotoluene (TNT) can be made by the (unbalanced) chemical reaction
C 7H5N3O6 + H2O. What mass of nitric acid (HNO3) is needed to react with 276 g of toluene (C7H8)?
a) 828 g
b) 566 g
c) 63 g
d) 189 g
e) 126 g
C 7H8 + HNO 3 →
5. What volume of HCl 0.100 mol/L is required to neutralize a solution containing 92.6 mg of Ca(OH)2?
a) 32.5 mL b) 12.5 mL c) 50.0 mL d) 25.0 mL e) 16.2 mL
6. The formula for aspirin (acetylsalicylic acid) is C9 H8 O4 . How much dioxygen is required for total combustion of 1 mole of aspirin to
carbon dioxide and water?
a) 9 mol O 2
b) 18 mol O2
c) 22 mol O2
d) 11 mol O2
e) 7 mol O2
7. Which one of the following represents an excited state electron configuration for a magnesium atom?
a) 1s22s22p63s23p1 b) 1s22s22p6
c) 1s 22s22p63s13p1
2
2
6
1
2
2
6
2
d) 1s 2s 2p 3s
e) 1s 2s 2p 3s
8. Which one of the following molecules contains a pair of atoms which share six electrons?
a) C2H6 b) CO2 c) C2H2 d) C 6H6 e) C2H4
9. Consider the two gases H2 and CO2 at 0°C. According to the kinetic theory of gases:
a) the molecules of both gases have zero kinetic energy at 0°C
b) the molecules of each gas have the same average speed at 0°C
c) all the molecules of both gases have the same speed at 0°C
d) the molecules of each gas have the same average kinetic energy at 0°C
e) all the molecules of both gases have the same kinetic energy at 0°C
10. A mixture of gases contains equal masses of He, H2, O 2 and CH4. If the partial pressure of CH 4 is 120 kPa, what is the
partial pressure of O2?
a) 480 kPa
b) 30 kPa
c) 120 kPa
d) 60 kPa
e) 240 kPa
11. Which one of the following elements has the largest atomic radius?
a) As
b) Br
c) P
d) S
e) Se
12. What is the shape of the ammonia molecule (NH3)?
a) linear
b) square
c) H--N--H (angles 90 deg)
d) a pyramid with a triangular base
|
e) a planar triangle with N at the centre
H
13. Which metal is extracted in large quantities in Canada from imported ore because of the availability of cheap hydroelectric
power?
a) Ni
b) Au
c) Cu
d) Al
e) Fe
14. The combustion of 1 mole of propane (C3H8) to CO 2 and liquid water liberates 2220 kJ of heat. If the heat of vaporisation
of water is 44 kJ/mol, how much heat is given off by the combustion of 1 mole of propane to CO2 and water vapour?
a) 1868 kJ
b) 2044 kJ
c) 2264 kJ
d) 2176 kJ
e) 2396 kJ
15. A "concentrated" aqueous solution of HCl is 37% HCl by weight and has a density of 1.19 g/mL. What is the
concentration of HCl in this solution?
a) 16.1 mol/L b) 12.1 mol/L c) 32.6 mol/L d) 9.1 mol/L e) 10.2 mol/L
16. Which one of the following compounds forms an acid solution in water?
a) CH3CH2COOH
b) CH3CH2NH2
c) CH3CH2OH
d) CH3CH2CH3
e) CH 3OCH3
17. If the equilibrium constant of the reaction A → B is less than one, then at equilibrium:
a) the concentration of product B exceeds the concentration of reactant A.
b) the rate of the forward reaction exceeds that of the reverse reaction.
c) the rate of the reverse reaction exceeds that of the forward reaction.
d) the concentration of product B equals the concentration of reactant A.
e) the concentration of reactant A exceeds the concentration of product B.
18. For the reaction 2 S(s) + 3 O2(g) → 2 SO3(g), which combination of equilibrium concentrations is equal to the
equilibrium constant Kc ?
a) [S]2[O2]3
[SO3]2
b) [O2]3
[SO3]2
c) [SO3]2
[S]2[O2]3
d) [SO3]
e) [SO3]2
[S][O2]
[O2]3
19. For the equilibrium H2(g) + I 2(g) æ 2 HI(g) at 200°C, ∆H = -9.5 kJ. What would be the effect of increasing the
temperature further?
a) the equilibrium constant (Keq ) of the reaction would increase
b) the concentration of HI would increase
c) the concentration of I2 would increase
d) there would be no effect on the equilibrium
e) the concentration of H2 would decrease
20. Which one of the following chlorine-containing compounds has been identified as a menace to the protective ozone layer in
the stratosphere?
a) DDT (C14H9Cl 5)
b) CF2Cl 2 c) HCl
d) HClO4
e) NaCl
21. Nitrous acid (HNO2) is a weak acid for which Ka = 4.0 x 10-4 mol/L? What is the concentration of un-ionized HNO2 in a
solution whose pH is 2.0?
a) 0.025 mol/L
b) 0.0063 mol/L
c) 0.25 mol/L
d) 0.0025 mol/L
e) 4 x 10-8 mol/L
22. In aqueous solution the ion Fe3+ is surrounded by six molecules of water to form the hydrated ion Fe(H2O)63+. If this
hydrated ion is a weak acid, what is its conjugate base?
a) Fe(H2O)5(H3O)3+
b) Fe(H2O)5(H3O)4+
c) Fe(H2O)5(OH)2+
3+
3+
d) Fe(H2O)6
e) Fe(H 2O)5(OH)
23. The solubility product of silver chromate (Ag 2CrO4) is 9.0 x 10-12 mol 3 L-3. The solubility of this salt is
a) 1.31 x 10-4 mol/L
b) 2.08 x 10-4 mol/L
c) 1.5 x 10-6 mol/L
-6
-6
d) 2.12 x 10 mol/L
e) 3.0 x 10 mol/L
24. For the reaction 2 NO(g) + 2 H2(g) → N2(g) + 2 H 2O(g), the following kinetic data were collected at 500°C:
Experiment
Initial [NO]
Initial [H2]
Initial rate
1
2
3
4
0.10 mol/L
0.10
0.25
0.35
The rate law for this reaction is
a) k[NO][H2]2
b) k[NO]2[H2]2
2
d) k[NO] [H2]
e) k[NO]2
0.20 mol/L
0.50
0.20
0.50
2.6 mol L-1 s -1
6.3
16.3
77
c) k[NO][H2]
25. If an oxidation-reduction reaction is described by the equation
Cu + 2 Ag+ → Cu 2+ + 2 Ag what is the equation for the oxidation half-reaction?
a) Cu2+ + 2e - → Cu
b) Ag+ + e - → Ag c) Ag → Ag+ + e +
d) Cu → Cu + e
e) Cu → Cu 2+ + 2e -
NATIONAL HIGH SCHOOL CHEMISTRY EXAMINATION (1999)
PART B - ESSAY QUESTIONS (Choose 2)
Answer TWO questions only in the form of scientific essays including any appropriate
equations, formulas and diagrams. Each question is of equal value. The judging of the
essays will be based on both factual accuracy and presentation. A clear, concise and wellorganized essay will be rated higher than a long rambling one which contains the same
information.
1. Carbon has a tendency to form polymeric chains such as polyethylene H-(CH2)n -H,
where n can be large. On the other hand, nitrogen does not form H-(NH)n -H and oxygen
does not form H-(O)n -H chains, where n > 2.
For the case n = 2: Draw Lewis diagrams for C,N,O chains. What are the common
names of these three molecules? Compare the physical states (gas, liquid or solid) of
these substances. In what state are they usually found in a laboratory? Compare the
chemical reactivity and stability of the three molecules. Give examples of how each is
used commercially.
For the general case: What do you think causes the difference in tendency to
polymerize? Discuss using concepts of bonding and bond energies where appropriate.
2. Sodium hypochlorite is a household reagent which is often used for swimming pool
maintenance.
a) Give the formula of sodium hypochlorite as well as its hydrolysis reaction in water.
Explain how this reaction affects the pH of the pool.
b) Hypochlorite ion undergoes a slow redox reaction in the pool, generating chlorate
and chloride ions. What are the oxidation states of the various species in solution?
Balance the equation for this reaction in basic solution. What type of redox reaction
is this?
c) In addition to hypochlorite, what other chemicals are commonly used to disinfect
pools? How do hypochlorite and these other chemicals kill bacteria?
3. a) How would one measure the rate of a chemical reaction? Choose a specific reaction
and describe an experiment to measure its rate.
b) The dependence of rate on reactant concentration is not always obvious. For
example the rate of the gas-phase reaction NO2 + CO → NO + CO 2 is given by v =
k[NO 2]2 and not v = k[NO2][CO] as one might expect. Suggest a reason why the first
rate law is correct.
c) How does the rate of a chemical reaction vary with temperature? How is the
activation energy obtained by studying this variation? Draw an energy diagram
which shows the activation energy. Explain the diagram in terms of the molecular
changes occurring.
Final Selection Examination 1999 (IChO)
Part C: Free Response Development Problems
1. The equilibrium constant for the reaction of Fe3+ and SCN– to form FeSCN2+ is done by examining the
absorbance of solutions. The absorbance is known to be directly related to the concentration of the
complex FeSCN2+ and follows Beer’s Law:
log(Po/P) = εbC = A
where Po is the radiant power of the incident beam upon the
solution containing Cmol/L of absorber, P is the power of the beam after it has traversed b cm
(usually 1 cm) of solution; and ε is a constant called “molar absorptivity”.
a) One literature source reports that at 580 nm, the wavelength of its maximum absorption, the complex
FeSCN 2+ has a molar absorptivity of 7.00 × 103 L cm–1 mol–1. Calculate the absorbance of a 4.00
× 10–5 mol/L solution of this complex at 580 nm when measured in a 1.00-cm cell.
b) A student was to determine the equilibrium constant for this reaction and followed the procedure
outlined, getting the specified results. A standard reference solution was prepared by mixing 18.0
mL of a 0.200 mol/L Fe3+ solution with 2.0 mL of 0.0020 mol/L SCN– The absorbance of this
solution was 0.520 . Several other solutions were prepared with the same 0.0020 mol/L SCN– and
dilute 0.0020 Fe3+ solutions. The data are provide only for #2.
Test Tube Number Fe(NO3)3 (mL)
KSCN (mL)
H2O (mL)
Absorbance A
#2
5.0
2.0
3.0
0.138
2+
Assuming [FeSCN ] and absorbance are related directly (Beer’s Law), the concentration of
FeSCN 2+ for any equilibrium system can be found by:
[FeSCN
2+
]eq =
A eq
Astd
2+
× [FeSCN
]std
Calculate the equilibrium constant for the reaction under experimental conditions.
c) For this same reaction the following results have been reported. Briefly account for each result on
the basis of equilibrium concepts.
I) Heat to 65-70°C; red colour decreases.
ii) Add -0.2 mol/L KSCN; red colour deepens.
iii) Add 1 mol/L NaOH; red colour changes and it becomes opaque.
iv) Add 0.1 M NaF; loss of colour and more transparent.
2. A steel-gray, lustrous metal was analyzed by X-ray diffraction. The results of the analysis indicated that
this metal crystallizes in a body-centered cubic (bcc) structure and has an estimated atomic radius of 125
pm. The density of the metal was found to be 7.14 g/cm3.
a) What is the volume of the bcc unit cell in cm3?
b) What is the metal?)
c) What is the coordination number of each metal atom in this bcc structure?
d) What type of holes (or interstices) is found in this bcc structure?
Give the name and the coordination number of the holes.
e) Calculate (in cm) the radius of the largest atom that can fit into the holes found in the crystal structure
of the metal mentioned in (b).
3. Organometallic complexes are defined as compounds containing at least one carbon-metal bond. A
certain organometallic complex contains carbon, hydrogen, and a metal from the first transition (one
metal atom per molecule). In a non-protic, complexing solvent like diethylether, this compound
dissociates into ions. In a non-polar solvent like benzene, the compound does not dissociate. Below
are data obtained from freezing-point depression and boiling-point elevation measurements, and
elemental analysis carried out on samples of this compound.
i) The freezing point (f.p.) of a benzene solution containing 1.514 g of the complex in 36.4 g of
solvent is 4.35°C (f.p. of pure benzene: 5.50°C; Kf of benzene: 5.12°C kg mol–1).
ii) The boiling point (b.p.) of a diethylether solution containing 0.4735 g of the complex in 10.0 g of
the solvent is 36.05°C (b.p. of pure diethylether: 34.50°C; Kb of diethylether: 2.02°C kg mol–1).
iii) Elemental analysis of the complex gives the following results: 64.88%C and 5.45%H.
a) In how many ions is the complex dissociated when dissolved in the complexing solvent?
b) Knowing that the metal contained in this complex can show very high oxidation states, what is this
metal?
c) Write the molecular formula of the complex.
4. In the upper atmosphere, ozone is produced from dioxygen: 3 O2(g) → 2 O3(g)
Thermodynamic data at 25°C
∆Hof /kJ mol–1
∆Gof /kJ mol–1
∆S o/J K–1 mol–1
O2(g)
--------205.138
O3(g)
142.7
163.2
239.93
a) Compute ∆Ho, ∆S o, and ∆Go for the production of ozone from dioxygen.
b) Is there a temperature at which this reaction becomes spontaneous when both dioxygen and ozone
are at standard pressure (1.00 atm or 101.3 kPa), i.e., when K o = 1? If so, what is this
temperature? If not, explain why one does not exist.
c) Assume an atmosphere with the partial pressure of dioxygen equal to 0.20 atm (20.26 kPa), i.e.,
P(O2) = 0.20 atm, and a temperature of 298 K. Below what pressure of ozone will ozone
production be spontaneous, i.e., will ∆G be less than zero?
d) In view of your answers to questions (a) to (c), how can the ozone layer form?
5.`The thermal decomposition of dinitrogen pentoxide was studied in both liquid dibromine (Reaction 1)
and in the gas phase (Reaction 2). In each case the reaction proceeds according to the equation:
2 N2O5 → 4 NO2 + O2
For the experiment in liquid dibromine the concentration of N2O5 varied with time as follows:
Time /s
0
200
400
600
1000
[N2O5] /mol/L
0.110
0.073
0.048
0.032
0.014
Below are the graphs obtained from these data:
[N2 O5 ] vs time
ln[N2 O5 ] vs time
1/[N2 O5 ] vs time
a) Confirm, by observing the graphs the order of this reaction.
b) Calculate the rate constant, k, for the reaction under these conditions.
c) In the gas phase, the first-order decomposition of N2O5 was found to have a rate constant of 4.8 ×
10–4 s–1. Calculate the half-life of this reaction.
d) If the initial pressure of N2O5(g) was 66.75 kPa in the gas phase reaction, what is the total pressure
of the system after 10 minutes?
e) The rate constant for the gas phase decomposition of N2O5 differs from that of the decomposition in
liquid dibromine. Coment on the difference in activation energy for the two processes.
O
6. a) Given that the pKa of ethanoic acid (CH3CO2H) is ca. 4.8 and the pKb of
methylamine (CH3NH 2) is ca. 3.4, draw the dominant form of the amino
acid alanine as it exists at:(3 marks)
i)
pH ca. 1
ii)
pH ca. 6
iii)
pH ca. 12
H3C
CH
C
O
NH2
alanine
b) The artificial sweetener aspartame (sold under the trade name Equal) is a modified dipeptide.
Aqueous acid hydrolysis of aspartame yields methanol (CH3OH) along with two amino acids.
Draw the structures of these two amino acid hydrolysis products.
O
O
O
C
CH2
CH
NH3
C
O
N
CH
H
CH2
C
OCH3
aspartame
c) i) Which of the following is NOT a nucleophile?
C
H2C
N
CH2
CH3OH
CH3NH2
CH3CH3
(CH3)O
H2C
ii) Which of the following is an electrophile?
H2
(CH3)B
(CH3)N
d) Draw the structures of the products of the following reactions.
Circle any of the products which will be optically active.
i)
NaOCH3 + CH3CH2Br
O
ii)
H
C
NaCN/H+
H
CH2OH
iii)
H
C
O
C
OH
CH2OH
H2/Pt catalyst
(2 products)
CH2
H
NATIONAL HIGH SCHOOL CHEMISTRY EXAMINATION 2000
PART A – MULTIPLE CHOICE QUESTIONS (60 minutes)
1. When the unstable nuclide
A. 223
B. 227
87 Fr
89 Ac
227
89 Ac
undergoes β decay, the resulting nuclide is:
C.
D. 227
E. 231
90Th
91Pa
227
88 Ra
2. A sample of H 2 (2.0 g) was burnt in Cl2 (75.0 g) containing a naturally occurring mixture of
isotopes. The resulting gas mixture was analyzed by mass spectrometry. The biggest peak
was found at which of the following mass numbers?
A. 36
B. 38
C. 70
D. 72
E. 74
3. Which of the following species has the greatest number of parallel spin electrons in the
ground state?
A. Cr
B. Mn
C. Fe3+
D. Co2+
E. Cu+
4. Which of the following species contains an element in an oxidation state that is not a whole
number?
A. VO43–
B. Mn2O3
C. S4O62–
D. Cl2O7
E. Cr2O72–
5. A certain substance contains 54.50% carbon and 9.09% hydrogen by mass. It molecular
formula could be:
A. CH 2
B. C2H4
C. C2H5OH
D. C3H7CHO
E.C3H7CO2H
6.
Which one of the following species has the largest radius?
A. Cl–
B. Ar
C. K
D. Ca
E. Cu+
7. Which of the following molecules has the smallest bond angle between its atoms?
A. H 2O
B. NH 3
C. SO3
D. CH 4
E. XeF4
8. The following sequence of reactions may be used to extract zinc from its sulfide ore:
2ZnS + 3O 2 → 2ZnO + 2SO 2
ZnO + C → Zn + CO
How many tonnes of zinc can be obtained from 20 tonnes of zinc sulphide, assuming that the
yield is 75%?
A. 5
B. 10
C. 12
D. 15
E. 20
9. Which one of the following substances in their standard state are held together by covalent
bonds ONLY?¤
A. C
B. AgBr
C. SiO2
D. NaOH
E. C6H12O6
10. Which one of the following substances has the highest boiling point?
A. CH 3COCH 3
B. CH3CO2CH3
C. CH3(CH2)2OH
D. CH 3(CH2)2CH3
E. CH3CHOHCH3
11. A solution of iodine was prepared by dissolving 12.70g of I2 and 20g of KI in water, and
making the volume up to 1 L. A 10.00 mL aliquot of this solution was titrated with standard
0.0500 M sodium thiosulphate solution, according to the following equation;
I2 + 2Na2S2O3 → Na2S4O6 + 2NaI
The volume of sodium thiosulphate used was 18.34mL. The molarity of the I2 solution in
mol/L was therefore:
A. 0.04585
B. 0.05004
C. 0.05453
D. 0.1001
E. 0.1205
12. Which one of the following compounds gives the highest pH when dissolved in water?
A. CH 3NH 2
B. CH3CO2H
C. CH3CONH 2
D. CH 3CO2NH 4
E. CH3NH 2CO2H
13. A concentrated aqueous solution of H2SO4 is 86% by mass and has a density of 1.78 g/mL.
50 mL of this solution is diluted to 1 L with water. What is the H+ ion concentration of the
dilute solution in mol/L? (All measurements are made at 25°C.)
A. 0.15
B. 0.51
C. 0.78
D. 1.01
E. 1.56
14. A container of 250 mL capacity contains 0.374 g of a particular gas at a temperature of
22.5°C and pressure of 1.006 bar. The gas could be:
A. H 2
B. He
C. HCl
D. H 2S
E. CH4
15. One Spring day the atmospheric temperature and pressure are 15.0°C and 101.23 kPa
respectively, and the air contains 2% by volume of water vapour. The next day the
temperature is still 15.0°C, but the pressure has dropped to 100.47 kPa. Given that the
average relative molecular weight of the gases in dry air is 28.94, the water vapour content of
the air is now:
A. 0%
B. 1%
C. 3%
D. 4%
E. 5%
16. All of the following reactions occur in the Earth’s stratosphere. Which one protects us most
from U-V radiation?
A. O 2 → O + O
B. O3 → O2 + O
C. O + O → O2
D. O + O2 → O3
E. O + O 3 → 2O2
17. Which of the following combustion reactions would give the maximum energy output per unit
mass of fuel plus oxidant when used to propel a rocket?
A. C(s) + O2(g) → CO2(g)
∆H = –393.5 kJ/mol
1
B. H2(g) + O2(g) → H2O(g)
2
1
1
C. H2(g) + F2(g) → HF(g)
∆H =–285.8 kJ/mol
D. CH 4(g) + 2O2(g) → CO2(g) + 2H2O(g)
E. C2H5OH(g) + 3O2(g) → 2CO(g) + 3H2O(g)
∆H = –890.3 kJ/mol
∆H = –1367.3 kJ/mol
2
2
∆H = –271.1 kJ/mol
18. Hydrogen is obtained industrially by the reaction of natural gas (methane) with steam in a
continuous flow system. The equation for the reaction is:
CH4(g) + H2O(g) → CO(g) + 3H2(g)
∆H = +206.1 kJ/mol
Which of the following would NOT increase the yield of hydrogen?
A. Increasing the pressure
B. Increasing the temperature
C. Removing the hydrogen as it is produced
D. Increasing the proportion of methane in the mixture
E. Increasing the proportion of water vapour in the mixture
19. What is the equilibrium law expression in terms of partial pressure for the following reaction?
C(s) + 2H 2O(g) → CO2(g) + 2H2(g)
∆H = +90.0 kJ/mol
A.
D.
(
pCO 2
)
1
2
• pH 2
B..
p H2O
(
)
2
pC • (2pH 2 O )
pCO 2 • 2pH2
2
E.
(
pCO 2 • p H2
)
2
(pH 2 O)
2
pC • ( pH 2O )
2
pCO 2 • (p H 2 )
2
C.
(
)
2
pC • (pH 2O )
pCO 2 • p H2
2
20. Ethyl ethanoate (0.20 mol) and water (0.6 mol) are mixed and left for several days to
equilibrate in the presence of an acid catalyst. At the end of this time 0.11 mol of ethanoic
acid is found to be present in the mixture. The equation for the reaction is:
CH3COOC 2H5 + H 2O → CH3COOH + C2H5OH
The equilibrium constant, Kc for the reaction is therefore:
A. 0.10
B. 0.27
C. 3.6
D. 4.0
E. 9.9
21. A group of students left a mixture of calcium hydroxide and water to equilibrate at 20°C.
They titrated the resulting saturated solution and found that it contained 0.040 mol/L of OH–
ions. The solubility product constant, Ksp{Ca(OH) 2} at this temperature is therefore:
A. 8.0 x 10–6
B. 1.6 x 10–5
C. 3.2 x 10–5
D. 6.4 x 10–5
E. 1.3 x 10–4
22. Hydrogen carbonate ions act as a buffer in blood. When acid comes in contact with hydrogen
carbonate ions, which of the following species is formed as the conjugate acid?
A. H 2O
B. H3O+
C. CO32–
D. HCO 3–
E. H2CO3
23. The base dissociation constant, Kb, of NH 3 is 1.8 x 10–5 at 25°C. The pH of a 0.1M solution
of NH 3 at this temperature is therefore:
A. 2.9
B. 4.8
C. 9.3
D. 11.1
E. 11.6
24. Two students performed a series of experiments to investigate the rate of the reaction
between magnesium and hydrochloric acid at room temperature. In each experiment they used
the same mass of magnesium but with different concentrations of acid (the acid always being
in excess). They measured the time taken for all the magnesium to react. Here are their
results:
Expt
Concentration of HCl, Time taken for all the
#
mol/L
Mg to react, s
1
2.00
25
2
1.50
30
3
1.00
100
4
0.50
400
The rate expression for this reaction is:
A. k[H+]
B. k[H+ ]2
C. k[Mg][HCl]
D. k[H+ ]–1
E. k[H+ ]–2
25. All of the following metals are used as protective coatings for iron and steel. Which one is
most likely to promote the rusting process? (E°(Fe 2+ /Fe) = –0.44 V)¤
A. Cadmium
(E°(Cd2+ /Cd) = –0.40 V)
B. Chromium
(E°(Cr3+ /Cr) = –0.74 V)
C. Nickel
(E°(Ni2+ /Ni) = –0.25 V)
D. Tin
(E°(Sn2+ /Sn) = –0.14 V)
E. Zinc
(E°(Zn 2+ /Zn) = –0.76 V)
THE CHEMICAL INSTITUTE OF CANADA
INSTITUT DE CHIMIE DU CANADA
“Chemists, engineers and technologists working together.”
“Les chimistes, les ingénieurs et les technologistes travaillant ensemble.”
_____________________________________________________________________
NATIONAL HIGH SCHOOL CHEMISTRY EXAMINATION 2000
PART B – ESSAY QUESTIONS (90 minutes)
Answer TWO questions only in the form of scientific essays, including any appropriate
equations, formulae and diagrams. Each question is of equal value. The judging of the essays will
be based on both factual accuracy and presentation. A clear, concise and well-organized essay
will be rated more highly than a long rambling one that contains the same information.
1. The Periodic Table and Periodicity
In this essay you might like to consider: (a) the history of the classification of the elements and
the development of the periodic table, especially the contribution of Mendeleev, (b) the
periodicity of physical properties on the macro scale, such as the “atomic volume”, density,
melting and boiling points, and structure and bonding of the elements, (c) the periodicity of
atomic scale properties, such as atomic and ionic radii, ionisation energies and electron affinities,
electronegativity, and oxidation number, and (d) the periodicity of the chemical properties of the
elements and their hydrides, oxides and chlorides. Note that you are not expected to have
memorized the values of the physical properties but you should discuss the trends across the
periods, and the reasons for these trends.
2. Water
In this essay you might like to consider: (a) the bonding and structure of water, (b) the phase
diagram of water, (c) the anomalous properties of water, and (d) its solvent properties. In each
case you should relate the properties of water with its importance in nature, eg. in the water
cycle and the weathering of rocks, and in living organisms and their habitats.
3. Petroleum
In this essay you might like to consider: (a) the way in which petroleum (crude oil) was formed,
(b) the chemical composition of petroleum, (c) the way in which petroleum is processed
industrially, (d) the uses of petroleum fractions, (e) the environmental problems of burning
petroleum products and how to limit these problems, and (f) the likelihood of all the petroleum
reserves being used up in the near future, and how we can replace petroleum as a raw material.
CHEMICAL INSTITUTE OF CANADA
and
CANADIAN CHEMISTRY OLYMPIAD
Final Selection Examination 2000
PART C: Free Response Development Problems
Time: 1.5 hours
60%
This segment has five (5) questions. While students are expected to attempt all questions for a
complete examination in 1.5 hours, it is recognized that backgrounds will vary and students will
not be eliminated from further competition because they have missed parts of the paper.
Your answers are to be written in the spaces provided on this paper. All of the paper, including this
cover page, is to be returned promptly to your Canadian Chemistry Olympiad Coordinator.
PART A
— PLEASE READ —
(
)
correct numbers
1.
2.
BE SURE TO COMPLETE THE INFORMATION REQUESTED AT THE
BOTTOM OF THIS PAGE BEFORE BEGINNING PART C OF THE
EXAMINATION.
STUDENTS ARE EXPECTED TO ATTEMPT ALL QUESTIONS OF
PART A AND PART C. CREDITABLE WORK ON A LIMITED
NUMBER OF THE QUESTIONS MAY BE SUFFICIENT TO EARN AN
INVITATION TO THE NEXT LEVEL OF THE SELECTION PROCESS.
3.
IN QUESTIONS WHICH REQUIRE NUMERICAL CALCULATIONS, BE
SURE TO SHOW YOUR REASONING AND YOUR WORK.
4.
ONLY NON-PROGRAMMABLE CALCULATORS MAY BE USED ON
THIS EXAMINATION.
5.
NOTE THAT A PERIODIC TABLE AND A LIST OF SOME PHYSICAL
CONSTANTS WHICH MAY BE USEFUL CAN BE FOUND ON THE
DATA SHEET PROVIDED WITH THIS EXAMINATION.
25 x 1.6 = ....... /040
PART C
1.
............... /012
2.
............... /012
3.
............... /012
4.
............... /012
5.
............... /012
TOTAL ......... /100
NAME
_______________________________ SCHOOL ___________________________
(Print Clearly)
CITY ______________________________
PROVINCE _________________________
Date of birth:
Exam Supervisor _____________________
Home Telephone number: (
) - _____________ Years at a Canadian high school _____
Male ❐
Canadian Citizen ❐
Landed Immigrant ❐
Visa Student ❐
Female ❐
Part C of Final Selection Examination (IChO 2000)
1. a) In 1828 Friedrich Wöhler found that the organic compound urea could be made by
evaporating an aqueous solution containing the inorganic compound ammonium cyanate,
thus repudiating the concept of "vitalism" which had held that organic compounds could
only be formed by living systems. The rate of this reaction has now been examined in an
aqueous solution containing 22.9 g of ammonium cyanate in 1.00 L of solution.
NH 4 CNO → CO(NH2 )2
Given the following data, what is the order of the reaction and the mass of ammonium
cyanate left after 200 min?
T/min
0
20
50
65
150
NH 4 CNO /g
22.9 15.9 10.8 9.1
5.2
Canadian Chemistry Olympiad
Page 7
Part C of Final Selection Examination (IChO 2000)
1. b) A typical urine sample contains 2.3% by mass of the base urea, CO(NH2 )2 . Urea is a
monoprotic base with a base dissociation constant, K b , equal to 1.5 x 10 –14 mol L–1 at
25°C. If, at 25°C, the density of a urine sample is 1.06 g cm–3 and the pH of the sample is
6.35, calculate the concentration of CO(NH2 )2 and of its conjugate acid CO(NH2 )NH 3 + in
the sample.
Canadian Chemistry Olympiad
Page 8
Part C of Final Selection Examination (IChO 2000)
2. HYDROLYSIS OF UREA
Urea, CO(NH 2 )2 , reacts with water to produce carbon dioxide and ammonia. Thermodynamic
data for the possible reactants and products are given below (neglect the solubility of carbon
dioxide and ammonia in liquid water).
a)
Compound
∆H fo (kJ mol –1 )
S o (J K –1 mol –1 )
CO(NH2 )2 (s)
-333.51
104.60
H2 O (l)
-285.83
69.91
H2 O (g)
-241.82
188.83
CO2 (g)
-393.51
213.74
NH 3 (g)
-46.11
192.45
Consider the hydrolysis of urea with H2 O (l) (Reaction A) and H2 O (g) (Reaction B)
respectively. Calculate ∆Ho , ∆S o , and ∆Go at 25o C for each reaction and specify whether
or not the reaction is spontaneous.
Canadian Chemistry Olympiad
Page 9
Part C of Final Selection Examination (IChO 2000)
2. b) Assuming that both ∆Ho and ∆S o are independent of temperature, find the temperature
above which Reaction A shall be spontaneous.
c) What major driving force favors both reactions in the forward direction? Justify your
answer.
d) Calculate K p at 25o C for each reaction and express these values with the proper units.
Canadian Chemistry Olympiad
Page 10
Part C of Final Selection Examination (IChO 2000)
3. COMPLEX IONS
PART I: Zinc Complex Ion
Zinc hydroxide is not very soluble in water, but in basic solution, it may dissolve as the
tetrahydroxozinc complex ion: Zn(OH)4 2-.
The solubility product constant of zinc hydroxide is K sp = 2.1 x 10-16 .
The formation constant (or stability constant) of Zn(OH)4 2- is K f = 2.8 x 1015 .
a)
If 150.0 mg of zinc hydroxide crystals are mixed with 250.0 mL of pure water, what
mass of crystals will remain undissolved and what will be the pH of the resulting solution.
Justify your answer by showing your calculations.
Canadian Chemistry Olympiad
Page 11
Part C of Final Selection Examination (IChO 2000)
b) If 150.0 mg of zinc hydroxide crystals are mixed with 250.0 mL of a 0.100 mol/L NaOH
solution, what mass of crystals will remain undissolved. Justify your answer by showing
your calculations.
Canadian Chemistry Olympiad
Page 12
Part C of Final Selection Examination (IChO 2000)
3.
COMPLEX IONS
PART II: Nickel Complex Ions
Several examples of Ni(II) complex ions appear below. They all possess an octahedral threedimensional structure.
Complex Ion A:
Complex Ion B:
Complex Ion C:
a)
Ni(NH 3 )3 (H2 O)3 2+
Ni(en)2 (NH 3 )2 2+
Ni(NH 3 )6 2+
where “en” = H2 N-CH 2 -CH2 -NH 2
Draw the possible structural isomers of complex ions A and B. Specify if any one
shows optical isomerism.
b) Complex ion C possess a pure octahedral geometry. Using crystal field theory, sketch the
energy-level diagram for the “d” orbitals of a metal atom in a pure octahedral field. Then,
fill in the d-electrons of the nickel ion using arrows to specify their spin. Label all the
orbitals in the diagram with the corresponding “d” notation (e.g. dxy ).
Canadian Chemistry Olympiad
Page 13
Part C of Final Selection Examination (IChO 2000)
4. Consider the half reactions shown below
Half reaction
Ce4+ (aq) + e– → Ce3+ (aq)
Cu2+ (aq) + 2 e– → Cu(s)
Sn2+ (aq) + 2 e– → Sn(s)
Ni2+ (aq) + 2 e– → Ni(s)
Al3+ (aq) + 3 e– → Al(s)
a)
E° (V)
+1.61
+0.34
–0.14
–0.25
–1.66
From the list above, identify
i) the strongest reducing agent
ii) the strongest oxidizing agent
iii) which metallic ion(s) can be reduced by Sn?
b)
An electrochemical cell with a potential difference of 1.59 V is prepared with aluminum
and nickel electrodes in their respective ionic solutions.
i)
Calculate the standard cell potential for the spontaneous reaction.
ii)
Given that the observed cell potential is 1.59 V, determine the
concentration of the aluminum ion if the concentration of the nickel ion is 2.0 M.
Canadian Chemistry Olympiad
Page 14
Part C of Final Selection Examination (IChO 2000)
c)
A small piece of freshly cleaned aluminum metal is placed in a solution of 1.0 M copper
nitrate, Cu(NO3)2, solution. After some time the blue colour of this solution decreases
considerably or disappears.
i) Describe what is happening, including any other observations that might be expected.
ii) Determine the free energy change, ∆G°, for this reaction.
Canadian Chemistry Olympiad
Page 15
Part C of Final Selection Examination (IChO 2000)
5. A) Complete the structural formulas located to the right of compound A in order to illustrate,
respectively, a diastereoisomer of A and the enantiomer of A.
O
H3 C
O
C
C
Br
CH2
C
Cl
C
C
C
CH2
CH2
C
H
O
C
C
C
C
C
CH2 OH
Compound A
Diastereoisomer of A
Enantiomer of A
Circle the most appropriate choices regarding Compound A:
i)
The stereochemistry assignments are: R
S
as well as
E
Z
ii)
The number of lone pairs of electrons is:
2
4
6
8
10
12
14
16
iii)
The degree of unsaturation is:
1
2
3
4
5
6
7
8
B)
i) Nuclear magnetic resonance (NMR) spectroscopy is a technique that can probe the structural
differences of various hydrogen atoms in a molecule. Assuming that free rotation is occurring
about all bonds and thus equivalent hydrogens are able to interconvert, indicate how many
different NMR signals you would expect to see in each of the following isomeric compounds.
H3 C
C
CH3
Br
Br
CH3
H3 C
CH2
C
CH3
C
CH2 Br
H
H
CH3
H3 C
iii) Circle the structure that represents a positively charged species and underline the negatively
charged species.
H3 CO
H2 C CH2
O
H
Canadian Chemistry Olympiad
O
H2 N
C
H
H2 C N N
Page 16
Part C of Final Selection Examination (IChO 2000)
ii)
Draw the structures of the major organic products necessary to complete the following
reactions. Pay close attention to stereochemistry. Indicate whether the product is achiral,
racemic or enantiomerically pure. In cases where a racemic mixture will be formed, draw
only one of the two possible enantiomers, but indicate that the product is racemic.
A
HBr
(concentrated)
HO
D
H
+
1) NaNH 2
CH3
K2 Cr2 O7 /H
B
2) CH3 CH2 Br
+
H /Heat
C
(End of Part C Examination)
Canadian Chemistry Olympiad
Page 17
NATIONAL HIGH SCHOOL CHEMISTRY EXAMINATION 2001
PART A - MULTIPLE CHOICE QUESTIONS (60 minutes)
1.
A solution of ethanol in water contains 20.0% by mass of ethanol (Mr = 46.1) and has a density of
0.96864 g mL-1. A lab technician measures out a 4.80 mL aliquot of this solution. What amount
(in moles) of ethanol does the aliquot contain?
A. 0.02
2.
C. NaCl
D. NaHCO3
E. Na2CO3
B. CH3CHO
C. CH3OCH3
D. CH3CO2H
E. CH3COCH3
Which of the following formulae can represent a pair of geometric (cis-trans) isomers?
B. HClCCH2
C. HClCCHCl
D. HCl2CCH2Cl
E. HCl2CCHCl2
Each of the following pairs of compounds can be reacted together to form a polymer. Which pair
gives Nylon?
A.
B.
C.
D.
E.
7.
B. H2O
A 20.0 g sample of an organic compound was found to give 27.50 g of carbon dioxide on
combustion. The compound could be:
A. Cl2CCH2
6.
E. 0.02017
The NaOH having absorbed CO2 from the air after its mass was measured
The NaOH having absorbed H2O from the air after its mass was measured
The pipette having been rinsed with water instead of NaOH
The flask having been rinsed with NaOH instead of water
The burette having been rinsed with water instead of HCl
A. CH3OH
5.
D. 0.0202
A mass of 4.021 g of NaOH is dissolved and made up to 1 litre of solution with water.
10.00 mL of this solution is pipetted into a flask and titrated with 0.050 M HCl solution from a
burette. A volume of 19.75 mL of acid had been used at the endpoint. This discrepant result could
be due to:
A.
B.
C.
D.
E
4.
C. 0.0201
In the titration of HCl (0.1 mol L-1) with Na2CO3 (0.1 mol L-1) which of the following species is
the major component of the solution at the methyl orange endpoint? The pKIn (298 K) of methyl
orange is 3.7.
A. CO2
3.
B. 0.020
H2N-CO-NH2 and CH2O
CH2=CH-CN and CH2=CH-CH=CH2
CH2=CH-CN and CH2=CH-O-CO-CH3
H2N-(CH2)6-NH2 and HO2C-(CH2)4-COOH
CH3-O-CO-C6H4-CO-O-CH3 and HO-CH2-CH2-OH
The following numbers represent the first four ionization energies of an element in kJ mol-1:
578; 1817; 2745; 11,578. Which of the following elements could it be?
A. Sodium
B. Magnesium
C. Aluminium
D. Silicon
E. Phosphorus
8.
Which one of the following species contains a partially filled d orbital?
A. Ag+
9.
B. Cu2+
D. Sc3+
E. Zn2+
Which one of the following pairs of elements can combine to give the strongest bond?
A. C, O
10.
C. Pb2+
B. F, F
C. Na, Cl
D. Na, K
E. O, O
Hydrogen can form a number of different kinds of bonds. Which of the following are never
found in pure substances?
A. Covalent bonds
B. Coordinate bonds
C. Hydrogen bonds
D. Ionic bonds involving H+ ions
E. Ionic bonds involving H- ions
11.
Which one of the following substances has the lowest boiling point at one atmosphere pressure?
A. C6H6
12.
B. (CH2)6
B. NH3
D. PCl3
E. SO3
B. CH4O
C. CH2O
D. H2SO4
E. C6H6O
B. N2O
C. NO
D. NO2
E. N2O3
The pH of an aqueous solution is 6.0 at 50oC. What is its hydroxide ion concentration in mol L-1?
(Kw = 5.5 x 10-14 at this temperature.)
A. 1.0 x 10-6
16.
C. PH3
Which one of the following compounds gives the lowest pH when dissolved in water?
A. NH3
15.
E. CH3CH2CH(CH3)2
Which one of the following molecular formulae could NOT represent a compound containing a
hydroxyl (-OH) group?
A. H2O
14.
D. CH3(CH2)3CH3
Which one of the following molecules has the greatest dipole moment?
(Electronegativity values for the elements concerned are: B = 2.0, Cl = 3.0, F = 4.0, H = 2.1,
N = 3.0, O = 3.5, P = 2.1, S = 2.5)
A. BF3
13.
C. C(CH3)4
B. 2.3 x 10-7
C. 1.0 x 10-8
D. 5.5 x 10-8
E. 7.8 x 10-8
What is the conjugate acid of glycine (aminoethanoic acid)?
+
A. H3O
D. H2N-CH2-CO2
B. H2N-CH2-COOH
+
E. H3N -CH2-CO2
+
C. H3N -CH2-COOH
17.
What is the approximate dissolved phosphate ion concentration in mol L-1 of a slurry of calcium
phosphate that is applied to a field as fertilizer, given KSP (Ca3(PO4)2) = 1.0 x 10 -26 at 25oC.
(Assume that the slurry is at 25oC and is in equilibrium.)
A. 2.5 x 10-6
18.
B. 3.5 x 10-6
C. 4.0 x 10-6
D. 5.0 x 10-6
E. 7.0 x 10-6
Consider the following equilibrium reaction:
CO(g) + 2H2(g) ⇔ CH3OH(l) ;
∆H = - 615.5 kJ mol-1
Which of the following changes in conditions would DECREASE the amount of methanol
produced:
A.
B.
C.
D.
E.
19.
20.
Increasing the proportion of carbon monoxide
Increasing the proportion of hydrogen
Increasing the pressure
Increasing the temperature
Removing the methanol as it is produced
Which one of the following pairs of reactants will give a neutral solution when mixed together in
equimolar amounts?
A. HCl (aq) + Pb(NO3)2 (aq)
B. H2SO4 (aq) + NaOH (aq)
D. CH3COOH (aq) + NaOH (aq)
E. CH3COOH (l) + CH3OH (l)
C. H2SO4 (aq) + K2O (s)
The following reaction takes place in a lime kiln:
CaCO3(s) → CaO(s) + CO2(g)
Given that ∆Hf (CaCO3(s)) = -1207 kJ mol-1; ∆Hf (CaO(s)) = -635.1 kJ mol-1;
and ∆Hf (CO2(g)) = -393.5 kJ mol-1, the energy change involved in producing
one tonne (1000 kg) of quicklime (CaO) is:
A. 1.78 x 103 kJ required
D. 1.00 x 106 kJ produced
21.
B. 1.78 x 106 kJ required
E. 3.18 x 106 kJ produced
C. 3.18 x 106 kJ required
What is the entropy change (in J mol-1 K-1) for the evaporation of water at standard ambient
temperature and pressure? Given:
∆H˚ f,298(H2O(l)) = -285.8 kJ mol-1 ∆G˚ f,298(H2O(l)) = -237.2 kJ mol-1
∆H˚ f,298(H2O(g)) = -241.8 kJ mol-1 ∆G˚ f,298(H2O(g)) = -228.6 kJ mol-1
A. -120
B. -0.12
C. 0.00
D. +0.12
E. +120
22.
Chlorofluorocarbons were widely used as refrigerants until it was discovered that they were
destroying the ozone layer. One of these, Freon 12, undergoes a series of reactions as shown
below (not in sequence). Which of these is the chain initiation reaction?
A. O• + O3 → 2O2
B. ClO• + O• → Cl• + O2
C. Cl• + O3 → ClO• + O2
D. CF2Cl2 → •CF2Cl + Cl•
E. •CF2Cl + •CF2Cl → C2F4Cl2
23.
Which one of the following reactions is NOT redox?
A.
B.
C.
D.
E.
24.
Br2 + H2O ⇔ HBr + HBrO
I2 + 2Na2S2O3 → 2NaI + Na2S4O6
Na3AsO3 + H2O2 → H2O + Na3AsO4
I2 + 6NaOH ⇔ NaIO3 + 5NaI + 3H2O
2K2CrO 4 + H2SO 4 ⇔ K2Cr2O 7 + K2SO 4 + H2O
The reaction between mercury(II) chloride and ethanedioate (oxalate) ions may be represented by
the following equation:
2HgCl2(aq) + C2O42-(aq) → 2Cl-(aq) + 2CO2(g) + Hg2Cl2(s)
If the rate of reaction at a particular stage of the reaction is 5.00 x 10-5 mol L-1 min-1 for HgCl2,
which is the correct rate of reaction at that time in terms of another component of the mixture?
A.
B.
C.
D.
E.
25.
5.00 x 10-5 mol L-1 min-1 for C2O425.00 x 10-5 mol L-1 min-1 for Cl1.14 x 10-6 g min -1 for CO2
2.40 x 10-3 L min-1 for CO2
1.05 x 10-7 g L-1 for Hg2Cl2
Two students set up a simple cell at room temperature and pressure with zinc as the anode and
nickel as the cathode. The relevant standard reduction potentials are:
Zn2+(aq) + 2e- ⇔ Zn(s) ;
Ni2+(aq) + 2e- ⇔ Ni(s) ;
Eo = - 0.76V
Eo = - 0.25V
If the concentration of the solution in the nickel half-cell is increased to 2.0 mol L-1 with respect to
Ni2+ ions and the concentration of the solution in the zinc half-cell is kept at
1.0 mol L-1 with respect to Zn2+ ions, then the overall cell potential will be:
A. more positive than + 0.51 V B. equal to + 0.51 V C. between + 0.51 V and - 0.51 V
D. equal to - 0.51 V
E. more negative than - 0.51 V
THIS IS THE END OF PART A OF THE EXAM
THE CHEMICAL INSTITUTE OF
CANADA
L’INSTITUT DE CHIMIE DU
CANADA
Chemists, engineers and technologists working together
Les chimistes, les ingénieurs et les technologistes travaillant ensemble
NATIONAL HIGH SCHOOL CHEMISTRY EXAMINATION 2001
PART B - ESSAY QUESTIONS (90 minutes)
Answer TWO questions only in the form of scientific essays, including any appropriate
equations, formulae and diagrams. Each question is of equal value. The judging of the essays
will be based on both factual accuracy and presentation. A clear, concise and well-organized
essay will be rated more highly than a long rambling one that contains the same information.
1.
Air Pollution
In this essay you should consider different sources of atmospheric pollution, the reactions taking
place in various parts of the Earth’s atmosphere, and the effects of pollution on plants, animals,
and buildings. You could also discuss how chemists and chemical engineers can help to improve
air quality.
2.
Catalysts
In this essay consider how catalysts can be used to alter the rate of chemical reactions, giving
examples of catalysts that are used in the laboratory, on an industrial scale, and in biological
systems. You could also discuss how a catalyst alters the energy profile of a reaction, and how it
changes the reaction mechanism.
3.
Polymers
In this essay consider some examples of polymers and the reactions that are used to produce
them, and discuss how polymers can be designed to have specific properties that enable them to
be used for different purposes. You could also compare some man-made polymers with similar
compounds that occur in nature.
CHEMICAL INSTITUTE OF CANADA
and
CANADIAN CHEMISTRY OLYMPIAD
Final Selection Examination 2001
PART C: Free Response Development Problems
60%
Time: 1.5 hours
This segment has five (5) questions. While students are expected to attempt all questions for a
complete examination in 1.5 hours, it is recognized that backgrounds will vary and students will
not be eliminated from further competition because they have missed parts of the paper.
Your answers are to be written in the spaces provided on this paper. All of the paper, including
this cover page, along with a photocopy of Part A of the examination, is to be returned promptly
to your Canadian Chemistry Olympiad Coordinator.
— PLEASE READ —
1.
2.
3.
PART A
BE SURE TO COMPLETE THE INFORMATION REQUESTED AT
THE BOTTOM OF THIS PAGE BEFORE BEGINNING PART C OF
THE EXAMINATION.
STUDENTS ARE EXPECTED TO ATTEMPT ALL QUESTIONS OF
PART A AND PART C. CREDITABLE WORK ON A LIMITED
NUMBER OF THE QUESTIONS MAY BE SUFFICIENT TO EARN
AN INVITATION TO THE NEXT LEVEL OF THE SELECTION
PROCESS.
IN QUESTIONS WHICH REQUIRE NUMERICAL CALCULATIONS,
BE SURE TO SHOW YOUR REASONING AND YOUR WORK.
4.
ONLY NON-PROGRAMMABLE CALCULATORS MAY BE USED
ON THIS EXAMINATION.
5.
NOTE THAT A PERIODIC TABLE AND A LIST OF SOME
PHYSICAL CONSTANTS WHICH MAY BE USEFUL CAN BE
FOUND ON THE DATA SHEET PROVIDED WITH THIS
EXAMINATION.
(
)
correct numbers
25 x 2.0 = ........../050
PART C
1.
..................../015
2.
..................../015
3.
..................../015
4.
..................../015
5.
..................../015
TOTAL.............../125
FINAL ............./100
NAME
_______________________________ SCHOOL ___________________________
(Print Clearly)
CITY ______________________________
PROVINCE _________________________
Date of birth:
Exam Supervisor _____________________
Home Telephone number: (
Male
) - _____________
Years at a Canadian high school ____
❐
Canadian Citizen ❐
Female ❐
Landed Immigrant ❐
Visa Student ❐
1. (15 marks)
1 a)
A compound of iron and chlorine was readily dissolved in water. An excess of silver
nitrate was added to precipitate the chloride ion as silver chloride. If a 0.270 g sample of
the compound gave 0.610 g of AgCl, what is the percent (%) chlorine in the compound of
iron and chlorine? What is the most probable identity of the compound of iron and
chlorine?
1 b)
A silver wire and a standard hydrogen electrode (SHE) were placed in a saturated
solution of silver oxalate, Ag2C2O4, The potential difference between the silver wire and
the SHE was measured as 0.589 V. Calculate the solubility product constant, Ksp, for
silver oxalate.
Given:
2H+(aq, 1M) + 2 e– → H2(g, 1 atm)
E° = 0.00 V
Ag (aq) + e → Ag(s)
E° = + 0.80 V
+
–
2.
(15 marks)
2 a)
Depleted uranium is primarily 238
, the remaining material after natural uranium has
92 U
235
been refined to remove most of the 92 U . The present controversy about its use in
armor-penetrating shells relates to both its chemical and radioactive properties.
206
Radioactive decay proceeds through a number of individual steps to eventually produce 82 Pb
A few of the initial reactions are illustrated below and you are expected to fill in the (7)
missing species and numbers in the blanks indicated to correctly complete each reaction.
238
92U
2 b)
α +
234
Th
0
β +
-1
0
Pa
β +
234
-1
In the February 8, 2001, Letters to Nature, measurement of stellar age from uranium
decay was reported by R. CAYREL, et al. They claim their cosmochronometer gives the
most direct age determination of the Galaxy.
Radioactive dating of meteoritic material and stars relies on comparing the present
abundance ratios of radioactive and stable nuclear species to the theoretically predicted
ratios of their production. 238U (half-life 4.5 Gyr) is in principle an age indicator, but even
its strongest spectral line, from singly-ionized uranium at a wavelength of 385.957 nm,
had previously not been detected in stars. They report a measurement in the very metalpoor star CS31082-001, a star that is strongly overabundant in its heavy elements. If their
derived uranium abundance was reported as 0.146, (i.e. the ratio of the radioactive U to
that theoretically predicted originally), what is their expected age of the Galaxy?
2 c)
The following initial rate data were obtained at 60°C for a reaction between
dibromoethane and potassium iodide in methanol. (In methanol, potassium iodide exists
mainly as KI molecules.)
C2H4Br2 + 3 KI → C2H4 + 2 KBr + KI3
Experiment
1
2
3
Initial conc.
C2H4Br2 mol L–1
0.50
0.50
1.50
Initial conc.
KI mol L–1
1.80
7.20
1.80
Initial rate
mol L–1 s–1
0.269
1.08
0.807
From these data, what is the rate expression for the reaction? Show your reasoning.
2 d)
The water flea Daphnia seems to have a heart that is capable of a limited number of
heartbeats and then it dies. These fleas live twice as long at 15°C as at 25°C. What is the
average activation energy for the reaction that controls the rate of the heartbeat of this
water flea?
3.
(15 marks)
3 a)
Spinel structures are found in mineral compounds having the general formula AB2O4.
These structures can be described as face-centered cubic (fcc) lattices of oxide ions
containing A and B metal cations.
Face-centered cubic crystal structure
i)
Assume that the oxidation states of A and B metals range from +1 to +6 (no fractional
values). What possible AB2 metal combinations would fit the general AB2O4 formula for
spinel compounds?
ii)
Assume that A and B are both cations from Row 3 (3rd Period).
Which cations of Row 3 allow an acceptable AB2 metal combination?
Should these cations be of approximately the same size? If not, which cation should be
the smallest one and why?
iii)
Magnetite, Fe3O4, possesses what is called an “inverse spinel” structure still based on fcc
lattice of oxide ions. Considering the different types of interstices (tetrahedral and
octahedral holes) in such a fcc lattice, calculate the ionic radii of the Fe ions, given that
the density of magnetite is 5.18 g cm-3 and that the ionic radius of oxide ions is 140 pm
(assume that oxide ions are closely packed and that Fe ions are fully occupying the hole
in which they are located).
3 b)
Let us compare the crystalline structures of sodium iodide and cadmium iodide. Both
structures are based on an fcc packing of iodide ions and both cations, Na+ and Cd2+, are
approximately of the same size. Sodium iodide is a brittle solid while cadmium iodide
can be used as a graphite-like lubricant. Give an explanation to account for the two very
different behaviours of sodium iodide and cadmium iodide.
4.
(15 marks)
4 a)
Chromium (VI) species are powerful oxidizers, which can oxidize primary alcohols to
carboxylic acids. The spectrophotometric determination of potassium dichromate
(K2Cr2O7), which shows an intense orange colour in solution, was for a long time the
basis for the testing of alcohol (ethanol CH3 CH2OH) in the breath / exhaled air of
suspected drunk drivers.
i) Write the balanced equation representing the oxidation of ethanol into acetic acid
(CH3COOH) by an acidified solution of potassium dichromate.
ii) A driver is arrested and asked to pass a “Breathalyser” test. A sample consisting of 56.5
mL of exhaled air is then bubbled into a spectrophotometric cell containing 3.00 mL of a
0.025% (w/v) potassium dichromate solution. The transmittance of the solution,
measured at the absorption wavelength of dichromate ion (450 nm), was 41.5% initially,
and 43.4% after bubbling the sample though the reaction cell. It is known that the alcohol
concentration in the blood stream is 2300 times higher than in the exhaled air, and that
the legal limit is 80 mg of alcohol per 100 mL of blood. Determine the concentration of
alcohol in the blood and state whether or not the driver should be charged with drunk
driving.
4 b)
A sample of 0.3657 g of a powder containing only barium nitrate (Ba(NO3)2) and calcium
nitrate (Ca(NO3)2) are dissolved in about 50 mL of water. Ammonia is added to the
solution to raise its pH, then an excess of sodium oxalate (Na2C2O4) is added to
precipitate the metals. The precipitate is then filtered, washed and transferred to a beaker
containing 50.00 mL of water. The solution is acidified to solubilise the precipitate before
being titrated with a solution of potassium permanganate (KMnO4) 0.0500 mol L–1. It was
found that 13.94 mL of the permanganate solution are required to reach the end point,
which is characterised by the pink coloration due to a slight excess of KMnO4.
Find the composition of the initial mixture.
Ksp:
BaC2O4 = 1.50 x 10-8
CaC2O4 = 2.34 x 10-9
Half-Reactions:
MnO4- + 8H+ + 5e- → Mn2+ + 4H2O
2CO2 + 2H+ + 2e- → H2C2O4
E° = +1.51 V
E° = -0.49 V
5.
(15 marks)
5 a)
A resonance structure is one of several valence-bond structures with localized electrons
that approximate the true structure of a compound that has delocalized electrons.
Draw two additional resonance structures of the amide shown below clearly indicating
the positions of any lone pairs of electrons and formal charges that may be present.
O
O
H
H 3C CH CH C N
H
H
H 3 C CH CH C N
H
5 b)
Write, in the boxes, the hybridizations of the oxygen atoms indicated in the ester below.
O
H3C
C
O CH3
5 c)
In the ester shown above in part b),
simultaneously could lie in the same plane.
5 d)
Knowledge of symmetry aids in predicting the number of products of a reaction and also
in interpreting the spectroscopic features of a molecule. Assume that free rotation is
occurring about all bonds in the molecule A below, and thus that equivalent atoms cannot
be distinguished.
CH3
H 3 C H 2C C CH3
A
is the maximum number of atoms that
CH3
i)
How many chemically different types of carbon atoms exist in A?
ii)
How many chemically different types of hydrogen atoms exist in A?
iii)
How many different dibrominated positional (also called constitutional) isomers
of A could be formed in the reaction of A with bromine?
iv)
Two of the possible dibrominated positional isomers of A can be chiral and thus
exist in the form of enantiomers (compounds not superimposable on their mirror
images). Draw these two different enantiomers.
5 e)
Clearly show the structure of the one major organic product of each of the following
reactions that all involve the loss of water (i.e. dehydration).
i)
O
C
CH3OH
OH
H
H 2O
+
+
OH
ii)
H3C
C O
H 2N-OH
H
H3C
+
H 2O
+
H 2O
+
iii)
+
CH3
H
OH
Heat
iv)
H 3C
C O
CH2 OH
CH2 OH
H 3C
H
+
H 2O
+
v)
Heat
HO 2C CH2 CH2 CO2 H
H 2O
+
END OF EXAMINATION
NATIONAL HIGH SCHOOL CHEMISTRY EXAMINATION 2002
PART A - MULTIPLE CHOICE QUESTIONS (60 minutes)
1. Someone has accidentally spilled battery acid on his or her skin. The first aid treatment for
this is to apply plenty of:
A. Salt
B. Water
C. Vinegar
D. Baking soda
E. Washing soda
2. Which one of the following substances, when dissolved in water, gives a solution with the
lowest pH?
A. Li2O
B. Na2O2
C. KO2
D. H2S
E. HI
3. What is the oxidation state of vanadium in the compound NH4VO3 (commonly known as
ammonium metavanadate)?
A. –1
B. +1
C. +3
D. +5
E. +6
4. A technician dissolves 62.425 g of CuSO4·5H2O (Mf = 249.7) in water and dilutes the
solution to 250.00 mL in a standard flask. He then measures out a 25.00 mL aliquot of the
solution. What amount (in moles) of CuSO4 does this aliquot contain?
A. 0.00100
B. 0.01600
C. 0.02500
D. 0.2500
E. 1.000
5. Which of the following statements is correct?
A. In an electrolytic cell oxidation takes place at a positive anode.
B. In an electrolytic cell oxidation takes place at a negative anode.
C. In an electrochemical cell reduction takes place at a positive anode.
D. In an electrolytic cell oxidation takes place at a positive anode.
E. In an electrochemical cell reduction takes place at a negative anode.
6. Which one of the following molecular formulae represents an alcohol?
A. CH3CHO
B. C2H5COOH C. (CH3)2O
D. (CH3)2CO
E. (CH3)3COH
7. Monocalcium phosphate (CaHPO4) is used as an acid in baking powders. Solutions of
CaHPO4 in water may contain a variety of species. Which of the following is the conjugate
base of the HPO42– ion?
A. Ca2+
B. OH–
C. H2O
D. PO43–
E. H2PO4–
8. In which one of the following compounds do all of the constituent atoms (or ions) obey the
octet rule?
A. NaH
B. BF3
C. PbI2
D. TiCl4
E. XeO3
9. The following reaction is used as the basis of the contact process (a step in the production of
sulfuric acid).
2 SO2(g) + O2(g) → 2 SO3(g);
∆H = –197 kJ·mol–1
Which one of the changes listed below could be used to increase the rate of production of
SO3 but would actually reduce the amount of SO 3 in the system if it were allowed to reach
equilibrium?
A. Heat the mixture.
B. Use V2O5 as a catalyst.
C. Increase the pressure of the mixture.
D. Increase the amount of oxygen fed into the reactor.
E. Increase the amount of sulfur dioxide fed into the reactor.
10. Which of the following substances will conduct electricity in the liquid state but not in the
solid state, and will not dissolve in water?
A. Ca
B. Cu
C. CuI
D. Cl3CCOOH
E. C6H12O6
11. Some students have been measuring the rate of reaction between 5.0 g of zinc granules and
100 mL of 1.0 M hydrochloric acid at room temperature. The equation for the reaction is:
Zn(s) + 2 HCl(g) → ZnCl2(aq) + H2(g)
Which of the following changes to the procedure would probably NOT increase the rate of
reaction?
A. Warming the HCl before adding the zinc.
B. Using zinc powder instead of zinc granules.
C. Using 50 mL of 2.0 M HCl.
D. Using 200 mL of 1.0 M HCl.
E. Using 100 mL of 1.0 M H2SO4.
12. Consider the following reaction, which is allowed to attain equilibrium in an enclosed
system:
CaCO3(s) → CaO(s) + CO2(g);
∆H = +178.3 kJ·mol–1
In addition to the temperature, the equilibrium constant for this reaction depends on:
A. The initial amount of CO2(g)
B. The initial amount of CaCO3(s)
C. The equilibrium amount of CO2(g)
D. The equilibrium amount of CaCO3(s)
E. The equilibrium amounts of CaCO3(s), CaO(s) and CO2(g)
13. Which one of the following molecular formulae can represent a pair of mirror image
isomers?
A. H2NCH2COOH
B. H2NCH(CH3)COOH
C. H2NCH2CH2COOH
D. H2NCH2COOCH3
E. (CH3)2CHCOOH
14. Which one of the following molecules has the largest bond angle?
A. CH4
B. NH3
C. H2O
D. SO2
E. CO2
15. Which one of the following molecules has the greatest dipole moment?
A. H2
B. HF
C. HCl
D. HBr
E. HI
16. Which one of the following molecules has the highest boiling point?
A. CH4
B. CH3Cl
C. CH2Cl2
D. CHCl3
E. CCl4
17. When 0.1 M aqueous solutions of the following pairs of reagents are mixed at room
temperature, which pair will NOT give a precipitate?
A. HCl + AgNO3
B. NaOH + CuSO4
C. CaCl2 + Na2CO3
D. H2SO4 + Ba(OH)2
E. NH4NO3 + K2CrO4
18. Benzoic acid (M f = 122.2) is used for preserving fruit juices. What is the approximate pH of
a saturated solution of benzoic acid in water, given that its solubility is 3.4 g/L, Ka = 6.40
× 10–5 (all measurements being made at 298 K)?
A. 1.8
B. 2.9
C. 3.4
D. 4.2
E. 5.7
19. Which one of the following indicators would be best to show the first endpoint of a titration
involving an approximately 0.1 M solution of Na2CO3 (in the flask) with an approximately
0.1 M solution of HCl (run into the flask from a burette)?
Indicator
pKIn
pH range
Acid çè alkaline
A.
Methyl violet
0.8
Yellow 0.0
to
1.6 Blue
B.
Bromophenol blue
4.0
Yellow 2.8
to
4.6 Blue
C.
Azolitmin (litmus)
–
Red 5.0
to
8.0 Blue
D.
Thymol blue (base)
8.9
Yellow 8.0
to
9.6 Blue
E.
Alizarin yellow R
12.5
Yellow 10.1 to 13.0 Orange
Questions 20 and 21 concern plaster of Paris, which is used for setting broken limbs. Its
formula is CaSO4·0.5H2O (Mf = 145.1). When water is added it sets to give gypsum,
CaSO4·2H2O (Mf = 172.2)
20. What is the minimum mass of water needed to set 0.500 kg of plaster of Paris?
A. 62.0 g
B. 93.1 g
C. 0.124 kg
D. 2.90 kg
E. 3.45 kg
21. What is the heat energy evolved (in kJ) when 0.500 kg of plaster of Paris sets? (Given that
∆Hf{H2O(l)} = –285.8 kJ·mol–1, ∆Hf{CaSO4} = –1434 kJ·mol–1, ∆Hf{CaSO4·0.5H2O} =
–1577 kJ·mol–1, and ∆Hf{CaSO4·2H2O} = –2023 kJ·mol–1)
A. 17.3
B. 59.6
C. 589
D. 1540
E. 2030
22. A well is sunk in a bed of rock containing fluorspar (CaF2). Given that Ksp(CaF2) = 4.0 ×
10–11 at 298 K, and assuming that the water in the well is saturated with CaF2, and that the
fluorspar is the only source of Ca2+ and F– ions, then the fluoride ion content of the water (in
mol·L–1 at 298 K) is:
A. 1.3 × 10–5
B. 2.2 × 10–4
C. 4.3 × 10–4
D. 6.3 × 10–6
E. 6.8 × 10–4
23. Which expression could be used to calculate an approximate enthalpy change of combustion
of methoxymethane (CH3-O-CH3) from standard bond enthalpy terms (E values)?
A. 6 × E(C-H) + 2 × E(C-O) – 6 × E(O-H) – 4 × E(C=O)
B. 3 × E(O-H) + 4 × E(C=O) – 6 × E(C-H) – 2 × E(C-O) – 3 × E(O=O)
C. 6 × E(C-H) + 2 × E(C-O) + 3 × E(O=O) – 6 × E(C-H) – 4 × E(C=O)
D. 3 × E(O-H) + 4 × E(C=O) – 6 × E(C-H) – 2 × E(C-O) – 3 12 × E(O=O)
E. 6 × E(C-H) + 2 × E(C-O) + 3 12 × E(O=O) – 3 × E(O-H) – 4 × E(C=O)
24. Which one of the following formulae represents a condensation polymer?
A. –(–CH(C6H5)–CH2–)n–
B. –(–CH2–CH=CCl–CH2–)n–
C. –(–C(CH3)(COOCH3)–CH2–)n–
D. –(–CH2–C(CN)H–CH2–CH(CN)–)n–
E. –(–NH–(C6H4)NH–CO–(C6H4)CO–)n–
25. The two liquids, methyl ethanoate (CH 3COOCH3) and trichloromethane (CHCl3) combine in
such a way that they form a single hydrogen bond between each pair of molecules. In an
experiment to determine the approximate strength of this bond, samples of the two liquids
were mixed in an insulated glass beaker, and the temperature was found to rise by 0.75°C.
Other data are given in the table below:
Mass, g
Amount of
Specific heat
substance, mol
capacity, J·g–1·K–1
CH3COOCH3
3.71
0.05
1.97
CHCl3
1.19
0.01
0.96
Beaker
60.00
–
0.6
The approximate strength of the hydrogen bond obtained by this experiment is (in kJ·mol–1):
A. 0.73
B. 3.6
C. 4.9
D. 36
E. 49
THIS IS THE END OF PART A OF THE EXAMINATION
THE CHEMICAL INSTITUTE OF CANADA
L’INSTITUT DE CHIMIE DU CANADA
“Chemists, engineers and technologists working together”
“Les chimistes, les ingénieurs et les technologistes travaillant ensemble.”
NATIONAL HIGH SCHOOL CHEMISTRY EXAMINATION 2002
PART B – ESSAY QUESTIONS (90 minutes)
Answer TWO questions only in the form of scientific essays, including any appropriate
equations, formulae and diagrams. Each question is of equal value. The judging of the essays
will be based on both factual accuracy and presentation. A clear, concise and well-organized
essay will be rated more highly than a long rambling one that contains the same information.
1.
Oil (Petroleum)
In 1872 Mendeleev visited North America. When he reported on this visit to his government he
said, “Oil is too valuable a material to be burned, and should be reserved as a source of
chemicals.” Discuss this statement in the light of modern day knowledge of petroleum and its
uses. In your essay you might like to consider (I) the chemical composition of petroleum, (ii) the
uses of petroleum fractions as fuels, (iii) other products derived from petroleum and their uses,
and (iv) alternatives to fuels and other products derived from petroleum. Illustrate your
arguments with specific examples wherever possible.
2.
The Extraction of Metals
In this essay you should discuss how the process used to extract a metal depends on the reactivity
of that metal, and you should summarize the specific processes used to extract several metals
with different reactivities. You may like to consider some of the following examples: gold,
copper, iron, aluminum and sodium. It is particularly important in this question to provide
equations for the reactions you describe.
3.
Bonding
In this essay you should describe the three main types of bonds (metallic, covalent and ionic),
and discuss how the type of bonding that holds a solid together can affect the physical properties
of that solid. Give examples of specific substances wherever you can.
CHEMICAL INSTITUTE OF CANADA
and
CANADIAN CHEMISTRY OLYMPIAD
Final Selection Examination 2002
PART C: Free Response Development Problems
60%
Time: 1.5 hours
This segment has five (5) questions. While students are expected to attempt all questions for a
complete examination in 1.5 hours, it is recognized that backgrounds will vary and students will
not be eliminated from further competition because they have missed parts of the paper.
Your answers are to be written in the spaces provided on this paper. All of the paper, including
this cover page, along with a photocopy of Part A of the examination, is to be returned promptly
to your Canadian Chemistry Olympiad Coordinator.
— PLEASE READ —
1.
2.
3.
PART A
BE SURE TO COMPLETE THE INFORMATION REQUESTED AT
THE BOTTOM OF THIS PAGE BEFORE BEGINNING PART C OF
THE EXAMINATION.
STUDENTS ARE EXPECTED TO ATTEMPT ALL QUESTIONS OF
PART A AND PART C. CREDITABLE WORK ON A LIMITED
NUMBER OF THE QUESTIONS MAY BE SUFFICIENT TO EARN
AN INVITATION TO THE NEXT LEVEL OF THE SELECTION
PROCESS.
IN QUESTIONS WHICH REQUIRE NUMERICAL CALCULATIONS,
BE SURE TO SHOW YOUR REASONING AND YOUR WORK.
4.
ONLY NON-PROGRAMMABLE CALCULATORS MAY BE USED
ON THIS EXAMINATION.
5.
NOTE THAT A PERIODIC TABLE AND A LIST OF SOME
PHYSICAL CONSTANTS WHICH MAY BE USEFUL CAN BE
FOUND ON THE DATA SHEET PROVIDED WITH THIS
EXAMINATION.
(
)
correct numbers
25 x 1.6 = ......... /040
PART C
1.
................... /012
2.
................... /012
3.
................... /012
4.
................... /012
5.
................... /012
TOTAL ............ /100
Name
_____________________________
School _____________________________
(Print Clearly)
City
_____________________________
Date of birth
Home Telephone (
Male
❐
Female ❐
Province _____________________________
E-Mail _____________________________
) - _____________________
Canadian Citizen ❐
Years at a Canadian high school ____
Landed Immigrant ❐
Passport valid until September 2002 ❐
Nationality of Passport
Visa Student ❐
1.
(12 marks)
When H2S is dissolved in water it is about saturated at a concentration near 0.1 M. Three
species containing sulfur exist in this solution, their proportions depending on the acidity
of the solution: H2S, HS– and S2–. Given the following equilibrium constants:
H2S → H+ + HS–
HS– → H+ + S2–
Ka1 = 1.0 x 10–7
Ka2 = 1.3 x 10–13
a)
What is the concentration of the sulfide ion, [S2–], in a saturated 0.100 M solution of H2S
when for the solution the pH = 2.0?
b)
A solution contains the cations Mn2+, Co2+ , and Ag + at an original concentration of
0.010M each. Which of these ions will precipitate when the solution is saturated in H2S
and the pH adjusted to pH = 2.0 by adding HCl? Explain your answer.
Given:
MnS Ksp = 2.5 x 10–10
CoS Ksp = 4.0 x 10–21
Ag2S Ksp = 6.3 x 10–50
-2-
c)
How many grams of lead(II) sulfide, PbS, will precipitate from 1.00 L of a saturated
solution of lead(II) sulfate, PbSO4, if the concentration of sulfide ion, [S2–], is adjusted to
give a concentration of 1.00 x 10–17 M?
Given:
Pb SO4 Ksp = 1.6 x 10–8
PbS Ksp = 2.5 x 10–27
-3-
2.
(12 marks)
Consider the following reactions involving the destruction of ozone:
a)
For the decomposition of ozone:
O3 (g) + O (g) → 2 O2 (g)
Draw the structures for the ozone and dioxygen molecules. Use these structural models
and your understanding of bond energies to predict whether this reaction is endothermic or
exothermic under standard conditions. Explain your answer.
b)
Nitrogen monoxide, NO, is an atmospheric pollutant that destroys ozone, O3, in the
stratosphere. Here is the accepted mechanism for the process:
O3 + NO → NO2 + O2
NO2 + O → NO + O2
O3 + O → 2 O 2
slow
fast
net, or overall, reaction
Draw an energy profile (activation energy diagram, i.e., a graph or diagram of energy
versus reaction progress or pathway) for this mechanism. Include as many details as
possible.
-4-
c)
Identify any catalyst(s) or intermediate(s) in the mechanism above. Explain your answer.
d)
The activation energy for the decomposition of ozone promoted by nitrogen monoxide is
11.9 kJ mol–1 . The activation energy for the decomposition of ozone promoted by
chlorine atoms is 2.1 kJ mol–1. From the information given, which pollutant is a more
serious threat to the ozone layer, chlorine atoms or nitrogen monoxide. Explain your
answer, stating all assumptions made.
-5-
3.
(12 marks)
a)
Under aqueous acidic conditions, permanganate ions (MnO4 ) oxidizes oxalate ions
-
2-
(C2O4 ) to yield carbon dioxide and manganese (II) ions. Give the balanced equations
for the two half-reactions.
A sample of K3[Fe(C2O4)3]•3H2O is dissolved in 10.00 mL of dilute sulfuric acid, and is
titrated spectrophotometrically with 0.0500 M potassium permanganate. Using the
titration curve below, calculate the initial mass of the complex present in the sample.
Spectrophotometric Titration Curve
Blank corrected
absorbance (abs u.)
b)
0.80
0.70
0.60
0.50
0.40
0.30
0.20
0.10
7.32 mL
0.68 abs u.
3.56 mL
0.23 abs u.
0.00 mL
0.34 abs u.
0.00
0.00
1.00
2.00
3.00
4.00
5.00
6.00
7.00
Added volume of permanganate solution (mL)
-6-
8.00
c)
The spectrophotometer that was used for the titration cannot properly measure
differences in light intensity by less than 1%. Using the above data, calculate the minimal
concentration of the complex that can be accurately measured.
d)
Another sample weighing exactly 0.101g, and containing only the K3[Fe(C2O4)3]•3H2O
complex and FeCl3•6H2O is dissolved in dilute sulfuric acid. The resulting solution is
mixed with a zinc amalgam to reduce all iron (III) ions to iron (II) ions. The solution is
then titrated against 0.0500 M potassium permanganate, and the equivalence point is
detected after the addition of 3.31 mL. Calculate the initial composition of the sample.
-7-
4.
(12 marks)
a)
Aldehydes and ketones react with alcohols to eventually form acetals and ketals.
O
H 3C
C
OCH3
HO
CH3 OH
R
an aldehyde R = H
H
+
H3C
C
CH3 OH
R
a hemi-acetal R = H
H
H 3C
+
C
R
an acetal R = H
a hemi-ketal R = CH3
a ketone R = CH3
OCH3
CH3 O
a ketal R = CH3
A number of oxygen functions are present in the structure below. Using the example
above as a guide, indicate the positions of the TWO aldehyde/ketone derivatives by
drawing an arrow to the carbon atoms of the former carbonyl (C=O). Indicate whether
the group is a hemi-actetal, hemi-ketal, acetal or ketal.
H
O
O
O
O H 3 CO
H
O
CH2 OCH3
HO
O
CH3
CH3
CH2 OCH3
H
H
O
O
OCH3
O
b)
A resonance structure is one of several valence-bond structures with localized electrons
that approximate the true structure of a compound that has delocalized electrons.
Complete the templates below to show three major resonance structures of the ester
shown below by clearly adding any missing bonds, lone pairs of electrons and formal
charges that may be present.
H
H C
H
O
C
H
O
C H
H
H
H C
H
-8-
O
C
H
O
C H
H
H
H C
H
O
C
H
O
C H
H
c)
Optically active compounds are not superimposable upon their mirror images. Threedimensional awareness is important in predicting optical activity. Complete the
structures below by adding an H and an OH group to each unspecified bond to generate
an optically active and a non-optically active system. Note the three-dimensional
convention used for the bonds.
CH3
CH3
H
OH
H
OH
= bond out of the page
= bond into the page
d)
CH3
CH3
Optically Active
NOT Optically Active
Place the following compounds in order of increasing acidity.
O
O
CH3 CH2 C OH CH3CH2 CH OH CH3 CH C OH
Br
CH3
A
B
C
least acidic
e)
CH3CH2 NH 2
D
most acidic
A compound that lacks a carbonyl group (C=O) and has the formula C14H24O reacts
rapidly with an excess of H2 in the presence of a catalyst to yield a new compound with
the formula C14H28O. The general formula of a non-cyclic alkane is CnH(2n+2).
The ORIGINAL compound contained
f)
double bond(s).
ring(s) and
Esters hydrolyze to form alcohols and carboxylic acids, whereas amides hydrolyze to
form amines and carboxylic acids. Write the products of the acidic aqueous hydrolysis
of the compound below that incorporates both an ester and an amide functionality.
O
H 3C
H2O
ester
OCH3
O
H 2O
H3C
NH2
amide
O
O
O
+
H , heat
N
+
H , heat
CH3 CO2 H + CH3OH
CH3CO2 H + NH4
H 2O
+
CH3
H , heat
-9-
+
5.
(12 marks)
Methanol (CH3OH) can be produced industrially from Synthesis Gas (CO and H2). The latter
can be obtained from methane (CH4; a major component of natural gas) and steam (H2O (g)).
The whole continuous process is illustrated in the flow chart below; Step A is the preparation of
Synthesis Gas and Step B is the preparation of methanol.
8
1
Synthesis
Gas Unit
(Step A)
3
2
Condenser
(25.0 ˚C)
4
Methanol
Unit
(Step B)
6
Condenser
(25.0 ˚C)
7
5
The feedstock of Step A is composed of pure methane gas (1) at a pressure of 250.0 kPa and a
temperature of 25.0˚C, and steam (2) at a pressure of 200.0 kPa and 100.0˚C (assume that steam
is pure water vapor). The flow rates of (1) and (2) are 55.0 L/s and 150.0 L/s, respectively.
Flowing out of Step A is a mixture (3) of Synthesis Gas and an excess reactant from the first step
that is condensed (5) at 25.0˚C. Methanol is produced in Step B from the feedstock (4) and the
effluent (6) from this reaction contains methanol and another excess reactant. The latter is
removed as (8) after condensation of pure methanol at 25.0˚C in (7).
Compound
Molar Mass
-1
(g mol )
16.04
Melting Point
(˚C)
Boiling Point
(˚C)
-183
-161
0.716 g L
H2O (l)
CO (g)
18.02
0
100
1.000 g mL
28.01
-205
-191.5
H2 (g)
2.016
-259.2
-252.8
1.250 g L
-----
CH3OH (l)
32.04
-98
64.7
0.791 g mL
CH4 (g)
Density at
25.0˚C
-1
-1
-1
-1
Assume ideal gas behavior; complete reactions in Steps A and B; and complete separation from
each condenser.
a)
Write the balanced chemical equation for the reaction of Step A.
Write the balanced chemical equation for the reaction of Step B.
b)
Which reactant is in excess after Step A?
Which reactant is in excess after Step B?
- 10 -
c)
Calculate the flow rates (in the proper units) at the following positions:
i)
The flow of the excess reactant at position (5) in L/s at 25.0˚C and 101.3 kPa:
ii)
The flow of the excess reactant at position (8) in L/s at 25.0˚C and 101.3 kPa:
iii)
The flow of pure liquid methanol at position (7) in L/s at 25.0˚C and 101.3 kPa:
END OF EXAMINATION
- 11 -