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June 2015 Main Examination, CHEM110/195: General Principles of Chemistry, UKZN, PMB
SECTION A - MULTIPLE CHOICE ANSWER SHEET
Choose the most correct answer for each of the multiple choice questions. Show your choice by
making a cross over the letter which corresponds to your answer, e.g. 1. X
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Page 1 of 22
June 2015 Main Examination, CHEM110/195: General Principles of Chemistry, UKZN, PMB
PART A – Multiple Choice Questions
Choose the most correct answer for each of the following multiple choice questions. Show your
answer on the sheet provided.
1.
Which of the following can have a variable composition?
i) Elements
ii) Compounds
a)
(i) and (ii) only
b)
(ii), (iii) and (iv) only
c)
(iii) and (iv) only
d)
(iv) only
iii) Homogeneous mixtures
iv) Heterogeneous mixtures
(1)
2.
When camping, you boil a pot of water on a campfire to make tea. Which of the following is
a chemical change?
a)
The water boils.
b)
The wood burns.
c)
The tea dissolves in the hot water.
d)
The pot melts from the heat of the fire.
(1)
3.
What is the most correct answer to the following calculation?
4.295 − 4.273
× log 6.15
18.012
a)
9.6 × 10–4
b)
9.64 × 10–4
c)
9.635 × 10–4
d)
9.6354 × 10–4
(1)
4.
Aluminium has a density of 2.70 g cm–3. If a cube of aluminium has a mass of 135 g, what is
the length of each side of the cube?
a)
50.0 cm
b)
7.07 cm
c)
3.68 cm
d)
0.271 cm
(1)
Page 2 of 22
June 2015 Main Examination, CHEM110/195: General Principles of Chemistry, UKZN, PMB
5.
Water has an accepted boiling point of 100 °C at standard atmospheric pressure. A student
measured the boiling point of water and recorded the following results:
Experiment
Number
1
2
3
4
5
Boiling Point
100.1
99.9
100.2
100.0
99.8
This set of results is best described as…
a)
neither accurate nor precise.
b)
accurate and precise.
c)
precise but not accurate.
d)
accurate but not precise.
(1)
6.
Which of the following contains more electrons than neutrons?
a)
b)
c)
d)
24
12
Mg 2+
33 2−
16
S
27
13
Al
75
33
As 3−
(2)
7.
Antimony (atomic symbol Sb) consists of two naturally occurring isotopes; 121Sb with mass
120.904 u and an abundance of 57.21% and 123Sb with mass of 122.904 u and an abundance
of 42.79%. Using this data, calculate the weighted average atomic mass of antimony.
a)
121.904 u
b)
121.760 u
c)
121.800 u
d)
122.000 u
(1)
8.
Which of the following contains the lowest percentage by mass of sulfur?
a)
H2S
b)
SO3
c)
SO2
d)
H2S2O7
(2)
Page 3 of 22
June 2015 Main Examination, CHEM110/195: General Principles of Chemistry, UKZN, PMB
9.
How many molecules of oxalic acid (H2C2O4) are there in a 16.5 g sample?
a)
1.10 × 1023 molecules
b)
3.29 × 1023 molecules
c)
3.64 × 1022 molecules
d)
9.93 × 1024 molecules
(2)
10.
What is the correct name of the compound Ti2(SO3)3?
a)
Titanium(II) sulfate
b)
Titanium(III) sulfide
c)
Titanium(II) sulfite
d)
Titanium(III) sulfite
(1)
11.
Which one of the following reactions is not a combination reaction?
a)
C + O2 → CO2
b)
2Mg + O2 → 2MgO
c)
CaO + H2O → Ca(OH)2
d)
CH4 + 2O2 → CO2 + 2H2O
(1)
12.
When the following equation is balanced, what is the coefficient of oxygen?
__NH3(g) + __O2(g) → __NO(g) + __H2O(g)
a)
3
b)
4
c)
5
d)
6
(1)
13.
Magnesium nitride reacts with water according to the following, balanced, equation:
Mg3N2 + 3H2O → 2NH3 + 3MgO
What mass of H2O (g) would be required to react with 5.00 g of magnesium nitride?
a)
15.0 g
b)
0.149 g
c)
2.68 g
d)
0.893 g
(2)
Page 4 of 22
June 2015 Main Examination, CHEM110/195: General Principles of Chemistry, UKZN, PMB
14.
Aqueous solutions of cobalt(II) nitrate and sodium phosphate are mixed together to produce
a precipitate. Identify the spectator ions in this reaction.
a)
Na+, PO43–
b)
Co2+, PO43–
c)
Na+, Co2+
d)
Na+, NO3–
(2)
15.
Arrange the following compounds of phosphorous in order of increasing oxidation number
of the phosphorous atom.
PH3
a)
PH3, P4, PF3, H3PO4
b)
P4, PF3, PH3, H3PO4
c)
H3PO4, PF3, P4, PH3
d)
PF3, PH3, H3PO4, P4
H3PO4
PF3
P4
(1)
16.
A solution of Ni(NO3)2 is prepared by dissolving 2.50 g of nickel(II) nitrate pentahydrate
(Ni(NO3)2·5H2O) in a 100.0 mL volumetric flask. What is the concentration of Ni(NO3)2 in this
solution?
a)
9.16 × 10–2 M
b)
1.37 × 10–1 M
c)
9.16 × 10–5 M
d)
1.37 × 10–4 M
(1)
17.
If 25.0 mL of a 0.345 M lithium carbonate solution is mixed with 37.1 mL of a 0.171 M
lithium carbonate solution, what is the final concentration of lithium carbonate?
a)
0.268 M
b)
0.139 M
c)
0.250 M
d)
0.241 M
(1)
Page 5 of 22
June 2015 Main Examination, CHEM110/195: General Principles of Chemistry, UKZN, PMB
18.
When a caesium salt is heated in a flame, a photon of light with energy 4.3 × 10–19 J is
emitted. Considering the table below, what colour is the photon?
Violet
Blue
Green
Yellow
Orange
Red
7.5 × 1014 s–1
6.5 × 1014 s–1
5.7 × 1014 s–1
5.2 × 1014 s–1
4.9 × 1014 s–1
4.3 × 1014 s–1
a)
Blue
b)
Green
c)
Yellow
d)
Orange
(1)
19.
Which atom in its ground state could have an electron with the following quantum
numbers: n = 3, l = 2, ml = 0, ms = –½?
a)
Al
b)
Mg
c)
Cl
d)
Sc
(1)
20.
What is the total number of electrons that can be accommodated in the third principle
energy level (n = 3)?
a)
8
b)
12
c)
18
d)
32
(1)
21.
Which of the following electronic configurations is incorrect?
a)
Mn = [Ar]4s23d5
b)
Mg = 1s22s22p63s2
c)
Mg2+ = 1s22s22p6
d)
Cl– = [Ne]3s23p4
(2)
Page 6 of 22
June 2015 Main Examination, CHEM110/195: General Principles of Chemistry, UKZN, PMB
22.
The following statements relate some concepts about chemical bonding and shapes of
simple molecules. Which of the statements is false?
a)
Covalent and ionic bonds are classified as primary bonds.
b)
In polar covalent bonds, the two atoms involved in bond formation have different
electronegativity values.
c)
A triple bond consists of one pi-bond and two-sigma-bonds.
d)
The lower the bond order, the longer the bond distance.
(1)
23.
Which one of the following statements best explains why the fourth ionisation energy of
aluminium is exceptionally high?
a)
Aluminium is a metal and does not lose electrons easily.
b)
The fourth ionization of aluminium involves removing an electron from the inner
core structure.
c)
Losing three electrons is impossible for the aluminium cation.
d)
The fourth ionisation energy is always greater than the second and the third
ionization energies.
(2)
24.
Arrange the following ions in order of increasing ionic radius: K+, P3–, S2–, Cl–.
a)
K+ < Cl– < S2– < P3–
b)
K+ < P3– < S2– < Cl–
c)
P3– < S2– < Cl– < K+
d)
Cl– < S2– < P3– < K+
(1)
25.
Carefully consider the nature of bonding in the following compounds:
(i) H2S, (ii) CaO, (iii) PCl5, (iv) BeCl2
Which compounds are ionic?
a)
(i) and (ii)
b)
(i) and (iii)
c)
(ii) and (iv)
d)
(iii) and (iv)
(2)
Page 7 of 22
June 2015 Main Examination, CHEM110/195: General Principles of Chemistry, UKZN, PMB
26.
Which of the following basic molecular shapes exhibits three different bond angles?
a)
Linear
b)
Trigonal planar
c)
Tetrahedral
d)
Trigonal bipyramidal
(1)
27.
Which type of bonding framework is dominant in solid water, ice?
a)
Covalent network
b)
Molecular bonding
c)
Ionic bonding
d)
Dative bond
(1)
28.
Which of the following shows the general trend in increasing strength of intermolecular
forces?
a)
London forces < dipole-dipole < H-bonding
b)
Dipole-dipole < H-bonding < London forces
c)
H-bonding < dipole-dipole < London forces
d)
London forces < H-bonding < dipole-dipole
(1)
29.
How many pi-bonds does the molecule CH3CN contain?
a)
1
b)
2
c)
0
d)
3
(1)
30.
Which of the following molecules is/are polar?
CO2
a)
NO2 only
b)
CO2, NO2 and COS
c)
CO2 and CS2
d)
COS and NO2
CS2
NO2
COS
(2)
Page 8 of 22
June 2015 Main Examination, CHEM110/195: General Principles of Chemistry, UKZN, PMB
31.
Calculate the height in meters of a column of liquid glycerol (density, d = 1.26 g cm–3)
required to exert the same pressure as 760 mmHg (d = 13.60 g cm–3).
a)
44.4 m
b)
8.20 × 103 m
c)
8.20 m
d)
70.4 m
(2)
32.
What volume of acetylene gas, C2H2, would be required at 0 °C and 1 atm to obtain a
200.0 g C2H2 sample?
a)
320.0 L
b)
172.1 L
c)
4480 L
d)
0.6304 L
(2)
33.
A balloon with volume 750 cm3 is filled with O2 (g) at 27 °C has a mass of 83.3 g. The mass of
the empty balloon is 82.1 g. Calculate the pressure of O2 (g).
a)
400 kPa
b)
125 kPa
c)
150 kPa
d)
75 kPa
(2)
34.
Assuming ideal gas behavior, which of the following gases would have the lowest density at
standard temperature and pressure?
a)
Kr
b)
N2
c)
CF2Cl2
d)
CO2
(1)
35.
In a group of non-metal elements, which element is least likely to form stable π bonds?
a)
the bottom element
b)
the second element
c)
the top element
d)
the middle element
(1)
Page 9 of 22
June 2015 Main Examination, CHEM110/195: General Principles of Chemistry, UKZN, PMB
36.
Which of the following would produce an acidic solution when dissolved in water?
Na2O CaO
a)
Na2O and CaO
b)
SO2 only
c)
CO, CO2, and SO2
d)
Na2O, CaO, and SO2
CO
CO2
SO2
(1)
37.
What are the products of the reaction between PCl3(g) and water?
a)
phosphoric acid and phosphorous acid
b)
elemental phosphorus and chlorine gas
c)
elemental phosphorus and hydrochloric acid
d)
phosphoric acid and hydrochloric acid
(1)
38.
Arrange the acids HOCl, HClO3 and HClO2 in order of increasing acid strength.
a)
HOCl < HClO3 < HClO2
b)
HOCl < HClO2 < HClO3
c)
HClO2 < HOCl < HClO3
d)
HClO3 < HOCl < HClO2
(1)
[50]
PART B – Written Answer Questions
Answer the following questions directly on the question paper in the space provided. Students are
requested to write neatly and clearly to ensure accurate marking.
QUESTION B1
1.
Iodine is known to sublime (change from a solid to a gas) readily. Draw a sketch to illustrate
the difference at an atomic level between iodine in the solid and the gas phase.
(2)
Page 10 of 22
June 2015 Main Examination, CHEM110/195: General Principles of Chemistry, UKZN, PMB
2.
Balance the following reaction in acidic media:
MnO2 + ClO3– → MnO4– + Cl–
(3)
3.
The compound urea (CO(NH2)2) can be synthesised according to the following reaction:
2NH3 + CO2 → CO(NH2)2 + H2O
If 50.0 g of NH3 and 50 g of CO2 are reacted in a particular experiment 47.7 g of urea is produced.
What is the percentage yield for this reaction?
(4)
[9]
Page 11 of 22
June 2015 Main Examination, CHEM110/195: General Principles of Chemistry, UKZN, PMB
QUESTION B2
1.
The percentage composition of the platinum-based anti-cancer drug cisplatin is summarised
in the table below:
Mass %
Pt
65.02%
Cl
23.63%
N
9.34%
H
2.02%
Use this information to determine the empirical formula of cisplatin.
(4)
Page 12 of 22
June 2015 Main Examination, CHEM110/195: General Principles of Chemistry, UKZN, PMB
2.
Combustion of 10.68 mg of a compound yields 16.01 mg CO2 and 4.37 mg H2O. The
compound contains C, H and O only. What is the percentage of each element in this
substance?
(4)
Page 13 of 22
June 2015 Main Examination, CHEM110/195: General Principles of Chemistry, UKZN, PMB
3.
One of the emission lines of hydrogen has a wavelength of 397 nm. If the transition is known
to be to the n = 2 energy level, in which energy level did the electron originate?
(3)
Question 4 continues overleaf…
Page 14 of 22
June 2015 Main Examination, CHEM110/195: General Principles of Chemistry, UKZN, PMB
4.
A student used a titration to determine whether an unknown sample was malonic acid
(CH2(COOH)2, molar mass = 104.1 g mol–1). The student weighed 1.08 g of the unknown acid
and transferred it to a 250.0 mL volumetric flask and prepared a standard solution. The
burette was filled with 0.09970 M NaOH solution and 20.00 mL aliquots of the acid solution
were titrated. The titration data are summarized in Table 1 below:
Table 1: Titration of 20.00 mL of acid solution against 0.09970 M NaOH solution.
Titration
1
2
3
Final Reading (mL)
17.73
17.35
17.91
Initial Reading (mL)
1.15
1.02
1.31
Titre (mL)
i)
Calculate the concentration of the acid (only use concordant titration results). The
acid and base react according to the following equation:
Acid(aq) + 2NaOH(aq) → Sodium salt(aq) + 2H2O(l)
(3)
ii)
Determine if the unknown acid is malonic acid.
(1)
[15]
Page 15 of 22
June 2015 Main Examination, CHEM110/195: General Principles of Chemistry, UKZN, PMB
QUESTION B3
1.
First ionization energies generally increase across a period in the periodic Table. Use
electron configurations of Beryllium, Be (Z = 4) and boron, B (Z = 5) to explain why Be has a
higher first ionization energy than B.
(2)
2.
Phosphoryl chloride (POCl3) is a colourless liquid used in the manufacture of phosphate
esters.
i)
Draw the Lewis structure of POCl3.
ii)
Determine the formal charge and oxidation state of P in your Lewis structure.
iii)
Determine the electron domain around the central P atom and predict the shape of
POCl3 using Valence Shell Electron Pair Repulsion theory
iv)
State the type of orbital hybridisation in the P central atom
i)
ii)
Page 16 of 22
June 2015 Main Examination, CHEM110/195: General Principles of Chemistry, UKZN, PMB
iii)
iv)
(4)
3.
Consider the Lewis structure of the CO32– anion and answer the questions that follow.
i)
Draw all the possible resonance structures of CO32–
ii)
Give the resonance hybrid structure of CO32–
iii)
What is the C–O bond order in the hybrid structure?
i)
ii)
iii)
(3)
Page 17 of 22
June 2015 Main Examination, CHEM110/195: General Principles of Chemistry, UKZN, PMB
4.
Explain the following observations
i)
Diamond is a non-metal, but harder than mercury which is a metal.
ii)
KOH dissolves in water (H2O), but insoluble in pentane
i)
ii)
(3)
[12]
QUESTION B4
1.
What is the total pressure (in bar) exerted by a mixture of 2.00 g of H2(g) and 8.00 g of
CO2(g) at 273 K in a 10.0 dm3 vessel?.
(4)
Page 18 of 22
June 2015 Main Examination, CHEM110/195: General Principles of Chemistry, UKZN, PMB
2.
A large flask was evacuated and found to weigh 141.225 g. It was filled with an unknown gas
to a pressure of 95.00 kPa at 26 °C and reweighed; its mass was 143.565 g. The flask was
then filled with water at 26 °C and found to weigh 942.781 g. (The density of water at 26 °C
is 0.9968 g cm–3.) Assuming that the ideal gas equation applies, determine the molar mass of
the unknown gas and its identity. (The unknown gas is one of the following: NH3, CO2, CS2,
or SO2).
(5)
Page 19 of 22
June 2015 Main Examination, CHEM110/195: General Principles of Chemistry, UKZN, PMB
3.
Halogen elements like fluorine and chlorine, F2 and Cl2, are reactive and thus of commercial
significance. Compounds of the halogens are equally important.
i)
Write a balanced chemical equation (including phases for all reagents and products)
for the reaction of fluorine with water; describe the redox changes occurring in the
reaction.
(2)
ii)
Write a balanced chemical equation for the reaction of chlorine with water and give
one commercial application for the reaction, explaining briefly how the process
works.
(2)
iii)
Hydrogen chloride gas may be produced by warming solid sodium chloride and
concentrated sulfuric acid in a test tube. Write a balanced chemical equation
(including phases for all reagents and products) for the reaction.
(1)
[14]
~END~
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June 2015 Main Examination, CHEM110/195: General Principles of Chemistry, UKZN, PMB
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June 2015 Main Examination, CHEM110/195: General Principles of Chemistry, UKZN, PMB
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