SPRINGFIELD CONVENT SENIOR SCHOOL
Gr 12 Physical Sciences PII (Chemistry)
19th
Thursday
June
150 marks
3 Hours
EXAMINER: B. Jansen
MODERATOR: G. Quinn
_______________________________________________________________________________________
SECTION A
QUESTION 1: MULTIPLE-CHOICE QUESTIONS
Four possible answers are provided for each of the following questions. Choose the correct answer. Write only
the letter next to the question number (1.1 – 1.10) on your script. Each question has ONE correct answer.
1.1
1.2
The ratio of the number of carbon atoms to the number of hydrogen atoms in a particular alkene can
be:
A
6 : 14
B
4:8
C
3:8
D
2:2
(2)
Poly(ethene) is manufactured when ethene is heated to a relatively high temperature under a high
pressure. The reaction is correctly illustrated in:
1 of 10
(2)
1.3
The molecular formula of 1,2-dichlorobutane is:
A
B
C
D
1.4
C4H10Cl2
C4H5Cl
C4H8Cl2
C4H6Cl2
(2)
The following potential energy curve represents the reaction given by the equation
2SO2 (g) + O2 (g)
2SO3 (g).
2 of 10
source: http://www.mathsandscience.com
The equation for the reverse reaction is 2SO3 (g)
values for H and Ea for the reverse reaction?
2SO2 (g) + O2 (g). Which of the following are the
H (kJ)
Ea (kJ)
A
+96
–20
B
+96
+40
C
–96
–136
D
+96
+136
(2)
1.5
Activation energy is the
A
B
C
D
1.6
minimum energy needed for molecules to react.
energy needed to form the covalent bond between two atoms.
amount of energy absorbed or released by a reaction.
amount of energy possessed by reacting molecules.
The following graph shows the volume of hydrogen gas produced against time.
3 of 10
(2)
Volume of hydrogen gas (cm3)
Time of reaction (min)
Which of the following statements about the above graph is INCORRECT?
A
The average rate of the reaction is about 7.25 cm3 min-1.
B
The average rate between t = 1 min and t = 3 min is about 13.5 cm3 min-1.
C
The instantaneous rate at t = 1 min is about 23.0 cm3 min-1.
D
The instantaneous rate at t = 2 min is about 11.0 cm3 min-1.
1.7
(2)
The following reaction reaches equilibrium in a closed container:
2A2X (aq)
+
BA2 (g)
3A2 (aq)
+
BX2 (s)
H < 0
The pressure in the container is then decreased.
What effect does this have on the rate of the reverse reaction and the concentration of A2?
Rate of reverse reaction
Concentration of A2
A
increases
increases
B
decreases
decreases
C
decreases
increases
D
increases
decreases
(2)
1.8
Consider the following equilibrium:
2NO2 (g)
N2O4 (g) + energy
The equilibrium will shift to the left as a result of:
A
adding a catalyst
B
increasing the volume
C
removing some N2O4
D
decreasing the temperature
4 of 10
(2)
1.9
1.10
The pH of 0,125 M NaOH solution is:
A
0.9
B
13.1
C
10.9
D
3.1
(2)
The Ka expression for hypochlorous acid does not contain which of the following?
A
H3O+
B
ClOC
HClO
D
H2O
Total for Section A
5 of 10
[20]
(2)
[20]
SECTION B
INSTRUCTIONS AND INFORMATION
1. Answer SECTION B in the ANSWER BOOK.
2. The formulae and substitutions must be shown in ALL calculations.
3. Round off your answers to TWO decimal places.
Question 2
The letters A to F in the table below represents six organic compounds.
A
B
C
But-1,3-diene
1-bromopropan-2-one
Propanoic acid
D
E
F
CH3
H
O
H
CH3
H–C– C – O–C–H
CH3 – C – CH3
CH3
H
2.1
2.2
2.3
H
OH
Write down the LETTER that represents:
2.1.1 a ketone
2.1.2 a cyclic hydrocarbon
2.1.3 a structural isomer of E
2.1.4 a product formed by the hydrolysis of an haloalkane.
(2)
(2)
(2)
(2)
Write down the IUPAC name of:
2.2.1 compound D
2.2.2 compound F
(2)
(2)
Write down the structural formula of:
2.3.1 compound A
2.3.2 compound B
(2)
(2)
[16]
6 of 10
Question 3
Organic solutions have wide variety of uses. The following information is given to you:
propan-2-ol
ethane-1,2-diol
(ethylene glycol)
(CH2OHCH2OH)
propanone
(acetone)
BOILING POINT (oC)
82.4
198
USES
rubbing alcohol
antifreeze
MOLECULAR MASS (g·mol-1
60
62
?
nail polish remover
58.1
3.1
Would propan-2-ol and ethane-1,2-diol (ethylene glycol) be isomers? Motivate your answer.
3.2
Provide an explanation for the observed difference in the boiling points of the ethane-1,2-diol
(ethylene glycol) and propan-2-ol. Refer to the type of intermolecular forces, molecular structure and
energy for your explanation.
(4)
3.3
How will the boiling point of acetone compare to the other two substances in the table. Write down
HIGHER THAN, LOWER THAN or EQUAL TO. Refer to intermolecular forces and energy to explain your
choice.
(4)
3.4
Containers of antifreeze contain such warnings as “Dispose of ethylene glycol properly” and “Keep out
of reach of children and animals”. Considering the chemical reactivity of alcohols, suggest a specific
reason for these types of warnings.
(2)
[13]
7 of 10
(3)
Question 4
4.1
The oxy-acetylene blowtorch shown
is widely used to weld and cut metals.
Acetylene or ethyne, when combined
with oxygen, burns at a temperature
of 3200 0C, the highest burning
temperature amongst the commonly
used gaseous fuels.
4.1.1 Write a balanced equation for the reaction between ethyne and excess oxygen.
(4)
4.1.2 Calculate the volume of oxygen required to react with a full 1,25 kg tank of ethyne at STP.
(7)
4.2
Some chemical reactions involving organic compounds are shown in the flow diagram below:
4.2.1
4.2.2
4.2.3
4.2.4
4.2.5
Name the type of reaction B and C.
(2)
List the reaction conditions for Reaction C.
(2)
Write down the structural formula of Y.
(2)
If reaction A involves Br2 and UV light, name the type of reaction as well as the compound X. (2)
Write down an equation for reaction D using structural formulae and circle the functional group of the
product.
(6)
8 of 10
4.2.6 Write down the IUPAC name of compound Z.
(2)
[27]
Question 5
Consider the repeating unit found in a polymer below:
5.1
Name the polymer.
(1)
5.2
Draw and name the monomer of this structure.
(3)
5.3
What type of polymerisation occurs in the formation of this molecule?
(1)
5.4
List TWO uses of this polymer.
(2)
[7]
Question 6
When sodium hydrogen sulphate decomposes, sodium sulphate, water and sulphur trioxide form. The
enthalpy change for the balanced reaction is -231.3 kJ
6.1
Write a balanced equation for this thermochemical reaction.
(4)
6.2
Is the reaction endo- or exothermic? Explain your answer.
(2)
6.3
Draw a fully labelled sketch graph illustrating the energy changes which would take place in this
reaction.
(4)
6.4
What quantity of heat is associated with the decomposition of 45.0 g of sodium hydrogen sulphate
according to this equation?
(5)
[15]
9 of 10
Question 7
Marble is composed mainly of the mineral calcite, which is pure calcium carbonate. Many old buildings were
built entirely of marble. With rising levels of pollution, acid rain is causing great damage to these buildings.
Sulphur dioxide is produced when high sulphur content coal is burnt. When the gas dissolves in atmospheric
water vapour, sulphurous acid (H2SO3) is formed and this attacks the marble.
7.1
Write a balanced equation for the reaction.
(3)
7.2
Students are curious about the effect of concentration on the rate at which the acid will dissolve
marble. Their science teacher provides them with two solutions of sulphurous acid: one with a
concentration of 0,001 mol.dm-3 and a second with a concentration of 0.01 mol·dm-3; and a small piece
of marble.
7.2.1 State a hypothesis for this investigation.
(1)
7.2.2 Explain the procedure they could use in their investigation. The apparatus listed below is set up
according to the diagram
Thermometer
Stopwatch
Beaker
Rubber stoppers (“corks”)
Rubber tubing
Measuring cylinder
Burette
Distilled water
(4)
7.2.3 Name a variable besides temperature that should be controlled in the investigation.
(1)
7.2.4 Write an equation to illustrate how the rate of the reaction could be calculated.
(1)
7.3
Based on the anticipated results, what advice could be given those attempting to retain the integrity of
old marble buildings?
(1)
[11]
10 of 10
Question 8
The following reaction is in equilibrium in a closed system at a temperature T:
C2H4 (g)
+
H2 (g)
C2H6 (g)
H < 0
8.1
During which industrial process is this reaction significant?
(2)
8.2
What does it mean when we say that a system is “in equilibrium”?
(2)
8.3
.
8.4
State Le Chatelier’s principle in words.
(3)
8.5
0,6 moles of C2H4 (g) and 0,5 moles of H2 (g) react in a 500 cm3 closed container. When equilibrium is
established at temperature T, it is found that 0,4 moles of C2H6 (g) are present in the container.
Determine the equilibrium constant at temperature T.
(6)
What would the effect on the yield of C2H6 be, by decreasing the temperature. Explain your answer.
(3)
8.6
Pressure in the container is increased by adding an inert gas at constant volume and temperature.
What would be the effect on …write only INCREASE, DECREASE or REMAINS THE SAME
8.6.1 the amount of ethane at equilibrium?
(2)
8.6.2 the magnitude of the equilibrium constant?
(2)
[20]
Question 9
As a class project, learners were asked to determine the amount of inert (unreactive) impurities in a
contaminated sample of anhydrous oxalic acid (H2C2O4).
One group of learners prepared a standard solution of sodium hydroxide (NaOH) by diluting 50 cm3 of a
1,63 mol·dm-3 solution in a 1 dm3 volumetric flask.
They then prepared a solution of the contaminated oxalic acid by dissolving 0,25 g of the oxalic acid in 75 cm 3
of water. The complete acid solution was then titrated against the NaOH solution and 40 cm3 of NaOH were
required to reach the equivalence point.
H2C2O4 + 2NaOH → Na2C2O4 + 2H2O
9.1
What is the concentration of the standard NaOH solution?
9.2
Use the information that the learners obtained and calculate the percentage purity of the oxalic acid
sample.
(10)
- 11 - of 10
(4)
9.3
What is meant by the ‘equivalence point’ of the titration?
(2)
9.4
Suggest an indicator which could be used in this titration. Explain your answer fully.
(5)
[21]
Total for Section B [130]
Grand Total [150]
- 12 - of 10
Memo
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
1.10
B
B
C
D
A
A
C
B
B
D 
2.1.1
2.1.2
2.1.3
2.1.4
B 
D 
C 
F 
(2)
(2)
(2)
(2)
(2)
(2)
(2)
(2)
(2)
[20]
(2)
(2)
(2)
(2)
2.2.1 1,3-dimethylcyclohexane 
2.2.2 2-methylpropan-2-ol 
2.3.1
H
H
H
(2)
(2)
H
H – C = C – C = C – H 
H O H
2.3.2
(2)
Br – C – C – C – H 
H
(2)
H
[16]
3.1
Not isomers  different molecular mass  different molecular formula 
3.2
propan-2-ol has one –OH group, ethylene glycol has two , more hydrogen bonds  stronger IM forces 
Less E need to break IMF, propan-2-ol has lower b pt. 
(4)
3.3
LOWER THAN 
Alcohols have hydrogen bonds, stronger than dipole-dipole in acetone; less energy needed to
overcome forces of acetone
(4)
3.4
Alcohols are flammable  and poisonous
- 13 - of 10
(3)
(2)
[13]
(4)
4.1.1 2C2H2 + 5O2  4CO2 + 2H2O
4.1.2 𝑛 =
𝑚
𝑀
1250
 =
26
 = 48.08 𝑚𝑜𝑙
C2H4: O2
2:5
48.08 : 120.19
Vol = n x 22.4  = 120.19 x 22,4 = 2692.31 dm3 = 2.69 m3 
(7)
Dehydrohalogenation/Elimination 
Hydrolysis/Substitution 
(2)
4.2.2 dissolve dilute NaOH in ethanoland heat
(2)
4.2.1 B
C

4.2.3
(2)
4.2.4 Substitution 
Ethane 
4.2.5

(2)



4.2.6 ethyl propanoate 
5.1
PVC  /polychloroethene
5.2
vinyl chloride /chloroethene
 circle functional group
 structural formulae
(6)
(2)
[27]
(1)

(3)
5.3
addition 
(1)
- 14 - of 10
5.4
PVC is used in construction, especially plastic piping. With the addition of a plasticiser it is also used in
clothing and upholstery and to replace rubber.
(2)
[7]
6.1
2 NaHSO4(s) ----> Na2SO4(s) + H2O(g) + SO3(g) 
6.2
exothermic  enthalpy ‹ 0 
∆H = -231.3 kJ
(4)
(2)
6.3
shape
axes
Ea
∆H
(5)
6.4
𝑚
 =
𝑀
𝑛=
45
120
 = 0.375 𝑚𝑜𝑙
0.375
2
(4)
x -231.3  = -43.37 kJ
(5)
[15]
7.1
H2SO3 + CaCO3   CaSO3 + H2O + CO2 
(balanced )
7.2.1 The greater the concentration, the faster the rate of reaction. 
(3)
(1)
7.2.2 Place the small marble chip in the beaker, cover it with sulphurous acid and then to invert the burette 
which has been filled with the acid and place the open end of the burette over the marble chip.
In this way, if it is done quickly, all gas produced, will be caught in the burette  where the volume of
gas and can be measured at regular intervals. 
(4)
7.2.3 mass of the marble 
(1)
7.2.4 reaction rate = volume of gas collected/ time 
(1)
7.3
Regularly rinse off building to dilute acid or other suitable
(1)
[11]
8.1
Hydrogenation/manufacture of margarine 
(2)
8.2
Rate of forward = rate of reverse concentrations remain the same 
(2)
- 15 - of 10
8.3
If the conditions (temperature, pressure, concentration) of an equilibrium system are changed, the reaction
that tends to cancel the effect of that change will be favoured.
(3)
8.4
8.5
Decrease in T slows both reactions down but exo less so, more C2H4 formed 
C2H4 (g)
Initial
m
M
n
0
0,4 mol
0,4 mol
-
-
-
0,4 mol
0,2 mol
0,1 mol
0,4 mol
0,4 mol.dm–3
0,2 mol.dm–3
0,8 mol.dm–3
n at equilibrium
 KC
[C2H6]/[C2H2][H2]
=
C2H6 (g)
0,5 mol
Formed
n
V
H2 (g)
0,6 mol
Used
C at eq c 
+
(3)
(0,8)
= 10 
(0,4)(0,2)
(6)
8.6.1 decreases 
8.6.2 remains the same 
9.1
n = cv  = 1.63 x 0.05  = 0.0815 mol
𝑐=
9.2
(2)
(2)
[20]
𝑐𝑎 𝑣𝑎
𝑐𝑏 𝑣𝑏
𝑛
𝑣
=
0.0815
1
 = 0.08 𝑚𝑜𝑙 · 𝑑𝑚-3
(4)
𝑛
= 𝑛𝑎
𝑏
𝑐𝑎 0.075
0.0815𝑥0.04
1
= 2
ca = 0.0217 mol·dm-3
𝑚
𝑐 = 𝑀𝑉 
m = 0.0217 x 90 x 0.075 = 0.1467 g
0.1467
percentage purity =
0.25
𝑥100 = 58.68%
9.3
Point where acid is completely neutralised by base 
9.4
Phenolphthalein 
- 16 - of 10
(10)
(2)
Salt formed when a strong base  and a weak acid  react is basic 
Need an indicator which changes colour in the basic range 
- 17 - of 10
(5)
[21]