Download 2013-2014

Class: _______ (
)
Name: ________________
Baptist Lui Ming Choi Secondary School
Final Examination (2013-2014)
Form 5 Chemistry
Date: 18-6-2014
Time: 8:40am–11:10am
(150 mins)
Total number of pages: 10
Section A
GENERAL INSTRUCTIONS
1.
2.
3.
4.
There are TWO sections, A and B, in this Paper. You are advised to finish Section A in about 45
minutes.
Section A consists of multiple-choice question in this question paper, while Section B contains
conventional questions printed separately in Question-Answer Book B.
Answers to Section A should be marked on the Multiple-choice Answer Sheet while answers to
Section B should be written in the spaces provided in Question-Answer Book B. The Answer Sheet
for Section A and the Question-Answer Book for Section B will be collected separately at the end
of the examination.
A Periodic Table is printed on the last page of Section A. Atomic numbers and relative atomic
masses of elements can be obtained from the Periodic Table.
1. Which of the following salts CANNOT be prepared by reacting a metal with a dilute acid?
A.
B.
C.
D.
Zinc sulphate
Silver chloride
Lead(II) nitrate
Iron(II) sulphate
2. Which of the following combinations of the reagents will NOT produce a gas?
A. magnesium + steam
B. zinc + solid citric acid
C. iron + orange juice
D. calcium + water
3. Which of the following compounds would react with ammonium sulphate on heating?
A. Concentrated sulphuric acid
B. Dilute hydrochloric acid
C. Sodium chloride solution
D. Sodium hydroxide solution
4. Which of the following does NOT cause acid rain?
A. NO
B. NO2
C. CO2
D. SO2
P.T.O.
F.5 Final (13-14)
Chemistry
P.2
5. The following set-up is used to collect hydrogen gas produced from the reaction between an acid and
magnesium.
hydrogen
magnesium
acid
Which of the following acids (with the same concentration) can produce hydrogen at the highest rate?
A. Citric acid
B. Carbonic acid
C.
D.
Ethanoic acid
Hydrochloric acid
6. Which of the following substances CANNOT react with ethene?
A. Bromine
B. Acidified potassium dichromate solution
C. Acidified potassium permanganate solution
D.
Hydrogen bromide
7. Which of the following statements about polypropene is/ are correct?
(1) Its repeating unit is
.
(2) It is a thermoplastic.
(3) It is non-biodegradable.
A.
(1) and (2)
B.
(1) and (3)
C.
(2) and (3)
D.
(1), (2) and (3)
8. Which of the following is the correct description of the shape of the molecule NH 3?
A. Trigonal planar
B. Tetrahedral
C. Trigonal pyramidal
D. Trigonal bipyramidal
To be continued.
F.5 Final (13-14)
Chemistry
P.3
9. Which of the following species would contain an unpaired electron?
A.
N 2O
B.
C.
D.
NO2
NO2+
NO
10. Which of the following statements about the reaction between acidified potassium dichromate solution
and sodium sulphite solution are correct?
(1) The oxidation number of sulphur increases.
(2) The colour of acidified potassium dichromate solution changes from orange to green.
(3) Dichromate ions are oxidized in the reaction.
A.
(1) and (2)
B.
(1) and (3)
C.
(2) and (3)
D.
(1), (2) and (3)
11. Which of the following substances react with both concentrated nitric acid and concentrated
hydrochloric acid?
A. S
B.
C
C.
Zn
D.
FeSO4
12. Consider the following chemical cell.
salt bridge soaked in
KNO3(aq)
electrode Y
electrode X
iron(II) sulphate
solution
acidified potassium
permanganate solution
Which of the following statements concerning the above chemical cell are correct?
(1) Electrons flow from electrode Y to electrode X through the external circuit.
(2) The electrodes can be made of platinum or graphite.
(3) The solution near electrode X changes from colourless to purple.
A.
(1) and (2)
B.
(1) and (3)
C.
(2) and (3)
D.
(1), (2) and (3)
13. Which of the following are the differences between a well-used zinc-carbon cell and a new one?
(1) The well-used one has a thinner zinc cup than the new one.
(2) The voltage of the well-used one is lower than that of the new one.
(3) The graphite rod of the well-used one is wetter than that of the new one.
A. (1) and (2)
B. (1) and (3)
C. (2) and (3)
D. (1), (2) and (3)
P.T.O.
F.5 Final (13-14)
Chemistry
P.4
14. The electrolysis of copper(II) sulphate solution was carried out using copper electrodes.
Which of the following graphs represents the mass of the copper cathode against time if a constant
current was used?
A.
B.
Mass of copper cathode
Mass of copper cathode
Time
C.
Time
D.
Mass of copper cathode
Mass of copper cathode
Time
Time
15. Which of the following statements concerning exothermic reaction are correct?
(1) In an exothermic reaction, the enthalpies of products are relatively lower than that of reactants.
(2) It involves releasing energy to the surroundings.
(3) Enthalpy change of the reaction is negative.
A. (1) and (2)
B. (1) and (3)
C. (2) and (3)
D. (1), (2) and (3)
16. Given that:
ΔH f [CO2(g)] = 395.0 kJ mol1
ΔH f [H2O(l)] = 286.0 kJ mol1
ΔH f [C2H5OH(l)] = 273.0 kJ mol1
Which of the following is the standard enthalpy change of combustion of ethanol,ΔH c [C2H5OH(l)]?
A.
408.0 kJ mol1
B.
954.0 kJ mol1
C.
1375 kJ mol1
D.
1921 kJ mol1
17. Which of the following processes is exothermic?
A.
B.
C.
D.
C8H18(l)  C4H8(g) + C4H10(l)
H2O(s)  H2O(l)
O2(g)  2O(g)
Cl(g) + e  Cl(g)
To be continued.
F.5 Final (13-14)
Chemistry
P.5
ΔHneut / kJ mol-1
18.
Acid A + Alkali X
-50.3
Acid A + Alkali Y
-54.2
Acid B + Alkali Y
-53.1
Acid B + Alkali Z
-56.4
What is the relative strength of alkalis X, Y and Z?
A. X > Y > Z
B. X > Z > Y
C. Z > Y > X
D. Z > X > Y
19. The reaction rate of which of the following reactions can be measured using a colorimeter?
A. Dissolving eggshells in sulphuric acid solution
B. The reaction of sulphur dioxide and bromine water
C. The reaction of ethyl propanoate and sodium hydroxide
D.
The reaction of silver and nitric acid
20. Zinc metal reacts with excess 1.0 M HCl according to the following equation:
Zn(s) + 2H+(aq)  Zn2+(aq) + H2(g)
Which of the following changes will increase the rate of evolution of H2(g)?
(1)
(2)
(3)
A.
Using zinc dust instead of chunks.
Using 200 cm3 of 1.0 M HCl in place of 100 cm3.
Using 2.0 M HCl instead of 1.0 M HCl.
(1) only
B. (2) only
C. (1) and (3) only
D.
(2) and (3) only
21. Which of the following statements explains correctly why antacids should be well chewed before
swallowing?
A. Gritted by teeth makes antacids hotter, so it will be more reactive.
B. The enzyme of the saliva can activate the antacids.
C.
D.
Chewing compresses the antacid molecules, so its concentration increases.
Chewing grinds the tablets into small pieces, so the surface area of antacids increases.
P.T.O.
F.5 Final (13-14)
Chemistry
P.6
22. After the addition of marble chips to an excess of dilute hydrochloric acid in a conical flask, each of the
following was measured and plotted against time on a graph.
Time (min)
If the reaction was complete in 2.5 minutes, which of the following, when plotted against time, would
give a graph like the one shown above?
A. Total mass of the conical flask and its contents
B.
C.
D.
Volume of carbon dioxide produced
pH of the solution
Temperature of the solution
23. In a Haber Process, N2(g) + 3H2(g)
2NH3(g), x mol of N2(g) and y mol of H2(g) are introduced into a V
3
dm container and allowed to reach equilibrium with NH3(g). At equilibrium, 2z mole of NH3(g) is found
in the reaction mixture. What is the equilibrium constant for the reaction?
A.
Kc =
4 z 2V 2
(x  z)(y  3z)3
B.
Kc =
2 zV
(x  z)(y  3z)
C.
D.
(x  z)(y  3z)3
Kc =
4 z 2V 2
(x  z)(y  3z)
Kc =
2 zV
24. Consider the following chemical equilibrium:
Cr2O72(aq) + H2O(l)
2CrO42(aq) + 2H+(aq)
yellow
Which of the following statement(s) is/are correct?
(1)
(2)
(3)
A.
Both Cr2O72(aq) and CrO42(aq) are present in the reaction mixture.
The solution becomes orange when dilute NaOH(aq) is added to the mixture.
The solution becomes yellow when dilute H2SO4(aq) is added to the mixture.
(1) only
B. (2) only
C. (1) and (3) only
D. (2) and (3) only
To be continued.
F.5 Final (13-14)
Chemistry)
P.7
25. For the following reaction:
Cu(OH)2(s)
Cu2+(aq) + 2OH(aq)
ΔH = +ve
2+
The equilibrium concentration of Cu (aq) would be increased by
(1) increasing the temperature.
(2) adding a few drops of dilute hydrochloric acid.
(3) adding a few drops of dilute sodium hydroxide solution.
A. (1) and (2)
B. (1) and (3)
C. (2) and (3)
D.
(1), (2) and (3)
26. Consider the following chemical equilibrium:
N2O4(g)
2NO2(g)
ΔH = +58 kJ mol1
Which of the following conditions would make the equilibrium mixture become darker?
A. Increasing the pressure
B.
C.
D.
Decreasing the temperature
Increasing the temperature but decreasing the pressure
Decreasing the temperature but increasing the pressure
27. Which of the following is the structural formula for methyl methanoate?
A.
B.
C.
D.
28. Which of the following compounds is the major product formed from the reaction between
buta-1,3-diene and hydrogen iodide?
A. 1,4-diiodobutane
B 2,4-diiodobutane
C. 1,3-diiodobutane
D. 2,3-diiodobutane
P.T.O.
F.5 Final (13-14)
Chemistry
P.8
29. Which of the following statements is/are correct?
(1) Two organic compounds with the same general formula must belong to the same homologous
series.
(2) Two organic compounds with one of the functional groups the same must belong to the same
homologous series.
(3) Two organic compounds with the molecular mass differing by 14 must belong to the same
homologous series.
A. (1) only
B. (2) only
C. (1) and (3) only
D. (2) and (3) only
30. Consider the following compound:
Which of the following functional groups does it contain?
(1) Carboxyl group
A. (1) and (2)
B.
(2) Carbonyl group
(1) and (3)
C.
(3) Amide group
(2) and (3)
D. (1), (2) and (3)
31. Arrange the following compounds in order of increasing boiling point.
Butan-1-ol, Butanone, Butanoic acid
A.
B.
C.
D.
Butan-1-ol  Butanone  Butanoic acid
Butanone  Butan-1-ol  Butanoic acid
Butanoic acid  Butanone  Butan-1-ol
Butanoic acid  Butan-1-ol  Butanone
32. Which of the following compounds could exhibit enantiomerism?
(1) 3-bromobut-1-ene
(2) 4-bromobut-1-ene
A.
(1) only
B.
(2) only
C.
(3) 2-bromobut-2-ene
(1) and (3) only
D.
(2) and (3) only
To be continued.
F.5 Final (13-14)
Directions:
Chemistry
P.9
Each question below (Questions 33 to 36) consists of two separate statements. Decide
whether each of the two statements is true or false; if both are true, then decide whether or
not the second statement is a correct explanation of the first statement. Then select one
option from A to D according to the following table:
A. Both statements are true and the second statement is a correct explanation of the first statement.
B. Both statements are true and the second statement is NOT a correct explanation of the first
statement.
C. The first statement is false but the second statement is true.
D. Both statements are false.
First Statement
Second Statement
33. The standard enthalpy change of solution
of a salt determines whether it is suitable
to be employed in instant hot packs or
instant cold packs.
The standard enthalpy change of solution of a
salt may be either positive or negative.
34. Ethanoic acid is a weak acid.
Although each molecule of ethanoic acid
contains four hydrogen atoms, only one is
ionizable.
35. The rate of reaction between sodium
thiosulphate and dilute hydrochloric acid
is measured by the time taken for the
‘blot out’ of the cross marked on the
white tile.
The time taken for the ‘blot out’ of the cross is
inversely proportional to the average rate of
formation of sulphur.
36. 2-Chlorobut-1-ene
isomerism.
2-Chlorobut-1-ene has a double bond.
shows
geometrical
END OF SECTION A
F.5 Final (13-14)
Chemistry
P.10
Class: _______ (
)
Name: ________________
Baptist Lui Ming Choi Secondary School
Final Examination (2013-2014)
Form 5 Chemistry
Date: 18-6-2014
Time: 8:40am–11:10am
(150 mins)
Total number of pages: 13
Section B
INSTRUCTIONS FOR SECTION B
1.
Answer all questions. Write your answers in the space provided.
2.
An asterisk(*) has been put next to the question where one mark will be awarded for effective
communication.
1.
(a)
A student wanted to investigate the properties of alkanes through combustion. He ignited a
sample of liquid pentane and liquid decane, C10H22, respectively.
(i)
State TWO differences in observation when these two different alkanes are ignited
respectively.
(ii)
Which one, liquid pentane or liquid decane, is more suitable for use as a fuel in lighters?
Explain briefly.
(3 marks)
(b)
(i)
Write an equation for the complete combustion of ethane in oxygen.
(ii)
What is the volume of air required to burn 1 dm3 of ethane?
(iii)
Apart from burning of fuels and respiration, state another human activity which would also
cause an increase in concentration of carbon dioxide in the atmosphere.
(4 marks)
P.T.O.
F.5 Final (13-14)
2. (a)
Chemistry
P.2
In an experiment to determine the concentration of ammonia solution, 25.00 cm 3 of the
ammonia solution was transferred into a conical flask and titrated against 0.10 M sulphuric acid.
A few drops of indicator were added. The titration results are listed in the table below:
Final reading (cm3)
Initial reading
(cm3)
1
2
3
4
15.90
16.70
18.40
18.50
0.00
1.50
3.10
3.40
(i)
Name the indicator suitable for this titration.
(ii)
What will be the colour change of the indicator at the end point?
(iii)
Calculate the reasonable average volume of sulphuric acid used.
(iv)
Calculate the molarity of the ammonia solution.
(6 marks)
*
(b)
Describe how a large crystal of the salt can be made based on the titration results in (a).
(4 marks)
To be continued.
F.5 Final (13-14)
3.
Chemistry
P.3
Phosphorus reacts with chlorine to form two possible products. One is polar and the another one is
non-polar. One of the products has the same shape as ammonia molecule.
(a) Write the chemical equations for the reactions involved.
(b)
(2 marks)
Draw the three-dimensional structures of the products. Show clearly the lone pair electrons of
the central atom if any.
(2 marks)
(c)
State with reason(s) which product is polar and which product is non-polar.
(2 marks)
P.T.O.
F.5 Final (13-14)
4. (a)
Chemistry
P.4
A student prepares a simple chemical cell as shown below.
salt bridge
graphite electrode X
AgNO3(aq)
graphite electrode Y
NaI(aq)
(i)
Write ionic half equations for reactions taking place at electrodes X and Y respectively.
(ii)
State any observable changes at electrodes X and Y respectively.
(iii)
What happens to the size of the voltage when the silver nitrate solution is replaced by
acidified potassium dichromate solution? Explain briefly.
(iv)
Explain why concentrated sodium chloride solution could not be used as the electrolyte in
the salt bridge.
(v)
Suggest a suitable electrolyte used in the salt bridge.
(7 marks)
To be continued.
F.5 Final (13-14)
4. (b)
Chemistry
P.5
An ore contains a mixture of copper and lead compounds, in which copper compound has a
larger proportion. A chemist extracts the metal ions by roasting the ore in air and then
dissolving the product in an acid. The solution that contains Cu2+(aq) and Pb2+(aq) ions is then
placed in an electrolytic cell as shown in the diagram below:
platinum electrode X
platinum electrode Y
solution containing
Cu2+(aq) and Pb2+(aq)
(i)
Which acid, hydrochloric acid or nitric acid, should be used for extracting the metal ions?
Explain your answer.
(ii)
Write half equations for the reactions at X and Y respectively when an electric current
flows in the cell.
(iii)
If the chemist used copper electrodes instead of platinum electrodes to set up the cell,
how would this affect the reaction? Explain your answer with appropratie half
equation(s).
(5 marks)
P.T.O.
F.5 Final (13-14)
5. (a)
Chemistry
P.6
A student set up an experiment to determine the enthalpy change of neutralization between
sodium hydroxide and hydrochloric acid. The set-up is shown below.
The student found that 40.0 cm3 of 0.6 M sodium hydroxide required 30.0 cm3 of hydrochloric
acid to achieve the maximum temperature rise of the mixture. The temperature change was
4.3C.
thermometer
beaker
HCl(aq) + NaOH(aq)
(i)
Suggest TWO improvements for the above set-up to achieve more accurate result.
(ii)
Calculate the enthalpy change of neutralization between HCl and NaOH with the help of
information given.
(Assume that the specific heat capacity and density of the solution are 4.2 J g 1 K1 and
1.0 g cm3 respectively.)
(6 marks)
To be continued.
F.5 Final (13-14)
5. (b)
Chemistry
P.7
Nitroglycerin (C3H5N3O9) is an oily and colourless liquid. It explodes when subjected to heat or
vibration.
(i)
Balance the following equation for the decomposition of nitroglycerine.
___C3H5N3O9(l)  ___ CO2(g) + ___ N2(g) + ___ H2O(g) + ___ O2(g)
(ii)
According to the literature, the standard enthalpy changes of formation of C3H5N3O9(l),
CO2(g) and H2O(g) are as follows:
Compound
ΔHf / kJ mol1
C3H5N3O9(l)
364
CO2(g)
394
H2O(g)
242
Using the given information, calculate the standard enthalpy change of decomposition of
nitroglycerin.
(4 marks)
P.T.O.
F.5 Final (13-14)
Chemistry
P.8
6. A student performed an experiment to study the reaction rate between 2.0 g of calcium carbonate
Volume of CO2 collected (cm3)
powder and 50.0 cm3 of 1.0 M hydrochloric acid (excess) at room temperature and pressure. In this
experiment, the volume of gas collected was recorded. The results were plotted as curve A in the
graph below.
curve A
Y
X
Time (min)
(a)
At which time, X or Y, is the reaction rate faster? Explain your answer by using collision theory.
(b)
(2 marks)
If the same experiment is done except using 25.0 cm3 of 1.0 M sulphuric acid (excess) instead.
Sketch the volume of CO2 collected against time in the diagram below and label the curve
as B.
Volume of CO2 collected (cm3)
(i)
curve A
Time (min)
(ii)
Explain why the shape of curve B is different from that of curve A.
(3 marks)
To be continued.
F.5 Final (13-14)
Chemistry
P.9
7. The operation of automobile airbags depends on the rapid decomposition of sodium azide, NaN 3, to
its elements.
(a) Write a balanced equation for this decomposition.
(b)
(1 mark)
If an airbag has a volume of 5.20 × 104 cm3, calculate the number of moles of nitrogen gas
required to fill it at room temperature and pressure. (Molar volume of gases at r.t.p. is
24.0dm3mol-1)
(1 mark)
(c)
Calculate the mass of sodium azide needed to provide such volume of nitrogen.
(2 marks)
(d)
If the decomposition is complete in
nitrogen in dm3 s1.
4010-3s,
calculate the average rate of formation of
(1 mark)
P.T.O.
F.5 Final (13-14)
8. (a)
Chemistry
P.10
The following graph shows the change of numbers of moles of the reactants and products with
time for the reaction: 2A(g) + B(g)
Number of moles (mol)

A2B(g) at 500C.
M
0.575
0.425
N
t1
(i)
0.15
B(g)
A2B(g)
A(g)
t2
What do the slopes at point M and point N at time t1 represent respectively?
(2 marks)
(ii)
Calculate Kc for the above reaction at 500C if the volume of the sealed container is 500
cm3.
(3 marks)
To be continued.
F.5 Final (13-14)
8. (b)
Chemistry
P.11
C(s) and H2(g) were allowed to attain equilibrium in an enclosed reaction vessel at 298 K. The
equation is shown below:
C(s) + 2H2(g)
CH4(g)
ΔH = 75 kJ mol1
State, with explanation, the effect of each of the following changes on the equilibrium position
of the above system and the value of Kc.
(i)
Increasing the temperature of the reaction vessel at constant pressure.
(ii)
Increasing the volume of the reaction vessel.
(4 marks)
9. Compound A is an alkane with the molecular formula C5H12 and it exhibits structural isomerism.
(a) Draw the structural formulae of isomers of A and state the type of structural isomerism.
(2 marks)
*
(b)
Arrange the boiling point of isomers of A in decreasing order. Explain your answer.
(4 marks)
P.T.O.
F.5 Final (13-14)
10. (a)
Chemistry
P.12
An organic acid Q is an isomer of butanoic acid. Give the systematic name of the organic acid Q.
(1 mark)
(b)
The structure of Z, another isomer of butanoic acid, is shown below:
HO
O
(i)
(ii)
Using ‘*’, label ALL chiral centre(s) in the above structure of Z.
Suggest a chemical test to show how to distinguish between Q and Z.
(3 marks)
11. Consider the following compounds:
Compound A
(a)
Compound B
Give the IUPAC name of compounds A and B.
(2 marks)
(b)
Write a chemical equation for each of the following reactions:
(i)
Mixing compound A with acidified potassium permanganate solution.
(ii)
Heating compound B with dilute hydrochloric acid under reflux.
(2 marks)
To be continued.
F.5 Final (13-14)
Chemistry
P.13
12. Consider the conversions of organic compounds shown below:
O
R
OH
dehydrating agent
CH3CH2 C CH2CH3
CH3CH2CH CH2CH3
X
Y
(a)
a mixture of alkenes
Z
Suggest a chemical test to distinguish between X and Y.
(2 marks)
(b)
Suggest what reagent R might be.
(c)
(1 mark)
The mixture Z contains two alkenes with the same structural formula. Draw the respective
structures of these two alkenes, and state their isomeric relationship.
(d)
(2 marks)
The alkenes in (c) can react with HCl to form an optically active chloroalkane. Write the
structural formula of this chloroalkane.
(1 mark)
END OF SECTION B
END OF PAPER
Baptist Lui Ming Choi Secondary School
Final Examination (2013-2014)
Form 5 Chemistry
Suggested Answers
Date: 18-6-2014
Time: 8:40am–11:10am
Section A
01
02
03
04
05
06
07
08
09
10
00
B
B
D
C
D
B
C
C
D
A
10
C
A
D
A
D
C
D
C
B
C
20
D
D
A
A
A
C
C
D
A
B
30
B
A
A
B
A
C
Section B
1. (a) (i)
(ii)
(b) (i)
(ii)
Decane burns with more sooty flame. [1]
Flame colour of decane is orange while that of pentane is yellow. [1]
Pentane is more suitable because it is more volatile / of lower boiling point. [1]
2C2H6(g) + 7O2(g)  4CO2(g) + 6H2O(l) [1]
From the equation, mole ratio of C2H6 : O2 = 1 : 3.5. Hence, the volume of oxygen required
to burn 1 dm3 of C2H6 = 3.5 dm3 [1]
Since air contains about 21% of oxygen, the approximate volume of air required to burn 1
dm3 of C2H6
= 3.5 dm3 
100
= 16.67 dm3 [1]
21
(iii) Deforestation [1]
2. (a) (i) Methyl orange [1]
(ii) From yellow to orange [1]
(iii) Ignore the first titration data.
Average volume of sulphuric acid used =
15.20  15.30  15.10 cm3
3
= 15.20 cm3 [1]
(iv) 2NH3(aq) + H2SO4(aq)  (NH4)2SO4(aq)
Number of moles of sulphuric acid used = 0.1 ×
15.20
mol
1000
= 0.00152 mol [1]
From the equation, mole ratio of NH3 : H2SO4 = 2 : 1
Number of moles of ammonia in 25.0 cm3 ammonia solution = 0.00152  2 mol = 0.00304
mol [1]
Molarity of ammonia solution =
0.00304
M = 0.122 M [1]
25.0
1000
P.2
2.
cm3
cm3
(b) Mix 15.20
acid and 25.00
ammonia solution without adding indicator. [1]
Heat the solution to make it more concentrated (saturated). [1]
Allow the solution to cool down and wait for a week. [1]
[1]: effective communication
3.
(a) 2P + 3Cl2  2PCl3 [1]
(b)
and
2P + 5Cl2  2PCl5 [1]
[1]
(c)
[1]
Both PCl3 and PCl5 have polar P-Cl bond.
PCl3 is polar as it is trigonal pyramidal and the dipole moment of the polar bonds cannot be
cancelled. [1] OR The central atom has a lone pair in its outermost shell and thus the three polar
P-Cl bonds are not on the same plane.
PCl5 is non-polar as it is trigonal bipyramidal and the dipole moment of the polar bonds can be
cancelled which results in zero net dipole moment. [1]
4.
X: Ag+(aq) + e  Ag(s) [1]
Y: 2I(aq)  I2(aq) + 2e [1]
(ii) Some silvery/grey solid deposits on electrode X. [1]
The solution around electrode Y changes from colourless to brown. [1]
(iii) The voltage becomes higher because acidified potassium dichromate solution is a stronger
(a) (i)
oxidizing agent than silver nitrate solution. [1]
(iv) Because the silver ions react with chloride ions to give a white precipitate, AgCl(s). [1]
(v) Potassium nitrate solution or other reasonable answers [1]
(b) (i) Nitric acid. It is because hydrochloric acid forms precipitates with lead(II) ions but nitric acid
does not. [1]
(ii) X: 4OH-  O2 + 2H2O + 4e- [1]
Y: Cu2+ + 2e-  Cu [1]
(iii) Copper electrode would be oxidized/dissolved at the anode(electrode X). [1]
Cu  Cu2+ + 2e- [1]
5.
(a) (i)
(ii)
The experiment should be carried out in an expanded polystyrene cup with a lid. [1]
The polystyrene cup should be surrounded by cotton wool. [1]
Mass of the reaction mixture = (30.0 + 40.0) cm3 × 1.0 g cm3 = 70.0 g
Heat released = m × c × T [1]
= 70.0 g × 4.2 J g1 K1 × 4.3 K
= 1264.2 J [1]
Number of moles of NaOH = 0.6 mol dm3 × 0.040 dm3 = 0.024 mol [1]
1264.2 J
Heat released per mole of H2O formed =
= 52 675 J mol1
0.024 mol
∴
the enthalpy change of neutralization = 52.7 kJ mol1. [1]
P.3
(b) (i)
(ii)
4C3H5N3O9(l)  12CO2(g) + 6N2(g) + 10H2O(g) + O2(g) [1]
ΔHr = 12 × ΔHf [CO2(g)] + 6 × ΔHf [N2(g)] + 10 × ΔHf [H2O(g)] + ΔHf [O2(g)]
 4 × ΔHf [C3H5N3O9(l)] [1]
1
ΔHr = [12 × (394) + 6 × 0 + 10 × (242) + 0  4 × (364)] kJ mol1
ΔHr = 5692 kJ mol1 [1]
1
∴ the standard enthalpy change of decomposition of nitroglycerin
=
 5692
kJ mol1
4
= 1423 kJ mol1 [1]
(a) As the concentration of the acid is higher at time X than at time Y [1], the reactant particles are
more crowded together. They will have a higher chance of effective collisions. [1] As a result, the
reaction rate is higher at time X.
(b) (i)
Volume of CO2 collected (cm3)
6.
(ii)
curve
Time
curve B
[1]
Time
The initial rate for the second experiment is higher than that of the first experiment. This
is because the concentration of [H+(aq)] ions in 1.0 M sulphuric acid (a dibasic acid) is
higher than that in 1.0 M hydrochloric acid. [1]
The volume of CO2 collected in the second experiment is less than that in the first
experiment. This is because calcium carbonate reacts with sulphuric acid to form insoluble
calcium sulphate, which prevents calcium carbonate from reacting with the acid
continuously. [1]
P.4
7.
(a) 2NaN3(s)  2Na(s) + 3N2(g) [1]
(b)
5.20  10 4
Number of moles of nitrogen gas =
mol = 2.17 mol [1]
24 000
(c)
Mole ratio of NaN3 : N2 = 2 : 3
Number of moles of NaN3 =
2.17  2
mol = 1.45 mol [1]
3
Mass of NaN3 needed = 1.45 × (23.0 + 14.0 × 3) g = 94.3 g [1]
(d)
8.
5.20  10 4
1000
Average rate =
dm3 s1 = 1300 dm3 s1 [1]
40  10 3
(a) (i)
Point M represents the rate of disappearance of B(g) at time t1. [1]
Point N represents the rate of formation of A2B(g) at time t1. [1]
(ii)
0.15 mol
= 0.3 mol dm3
0.5 dm 3
0.575 mol
[B(g)]eqm =
= 1.15 mol dm3
0.5 dm 3
0.425 mol
[A2B(g)]eqm =
= 0.85 mol dm3 [1]
0.5 dm 3
[ A2 B(g)] eqm
Kc =
[1]
[ A(g)] 2 eqm[ B(g)] eqm
[A(g)]eqm =
=
(b) (i)
(ii)
(0.85 mol dm 3 )
(0.3 mol dm  3 ) 2 (1.15 mol dm  3 )
= 8.21 mol2 dm6 [1]
As the forward reaction is exothermic, [1] an increase in the temperature of the reaction
vessel causes the equilibrium position of the system to shift to the left and the value of Kc
will decrease. [1]
As the numbers of moles of gases on the left-hand side of the balanced equation are
greater than that on the right-hand side, [1] an increase in the volume of the reaction
vessel causes the equilibrium position of the system to shift to the left. But the value of Kc
will remain unchanged because it is temperature dependent. [1]
P.5
9.
CH3
(a)
CH3CH2CH2CH2CH3
CH3
CH3CH2CH CH3
CH3 C CH3
CH3
[1]
Chain isomerism [1]
(b) Boiling point: pentane > methylbutane > dimethylpropane [1]
Pentane is a straight chain alkane without any branches which has the largest contact surface
area while dimethylpropane is like a sphere which has the lowest contact surface area. [1]
Van der Waals’ forces between pentane molecules is the strongest while that between
dimethylpropane molecules is the weakest. [1]
Thus, more energy is needed to separate the pentane molecules during the boiling process.
[1]: effective communication
10. (a) Methylpropanoic acid [1]
(b) (i) HO
*
(ii)
O [1]
Correct chemical reagent [1]
Correct observations with comparison between the tests on Q and Z [1]
Ca/Mg/Zn/Fe/metal
Observations: Q – colourless gas bubbles; Z – no change
carbonate/metal
hydrogencatbonate
Cr2O72-/H+
Observations: Q – no change; Z – orange to green
MnO4-/ H+
Observations: Q – no change; Z – purple to colourless
11. (a) A: trans-1,2-difluoroethene; B: ethanamide [2]
H
(b) (i) H
F
C C
F
+ [O] + H2O
H
F C
OH
F
C H
OH
[1]
(ii)
[1]
12. (a) Correct chemical reagent [1]
Correct observations with comparison between the tests on X and Y [1]
Cr2O72-/H+
Observations: X – no change; Y – orange to green
MnO4-/ H+
Observations: X – no change; Y – purple to colourless
(b) LiAlH4[1] in dry ether and then H+
(c)
Geometrical isomerism [1]
and
[1]
(d) CH3CHClCH2CH2CH3 [1]