WESTERFORD and CLAREMONT HIGH SCHOOL
Physical Science
GRADE 12
CHEMISTRY: PAPER 2
MAY 2014
EXAMINER:
P. BODENSTEIN
TIME:
MARKS:
2 HOURS
100 MARKS
INSTRUCTIONS
1.
Answer ALL the questions.
2.
Answer SECTION A on the ANSWER SHEET and SECTION B on the
folio provided. Start each new answer on a new sheet of paper.
3.
Number the answer in the same way that the questions are numbered.
Leave one line open between subsections of questions.
4.
Non-programmable calculators may be used. Appropriate mathematical
instruments may be used.
5.
Data sheets will be provided.
6.
Use black or blue ink only for your answers, other than sketches and
diagrams where a sharp pencil must be used.
7.
Give ALL the formulae used and show your working, including
substitutions. Your answer must be calculated correctly to two decimal
places.
8.
A penalty of 1% will be imposed for each instruction disregarded.
SECTION A
Answer this section on the ANSWER SHEET provided.
QUESTION 1: MULTIPLE-CHOICE QUESTIONS
Four options are provided as possible answers to the following questions. Each question has
only ONE correct answer. Write only the CAPITAL letter (A–D) next to the question number
(1.1–1.10) on the ANSWER SHEET provided.
1.1
A catalyst...
A
B
C
D
increases the activation energy of a reaction
is a liquid that speeds up a reaction
does not change ∆H in a reaction
is Pt in a halogenation reaction
(2)
1.2
Consider the structural formula of an organic compound below.
Which ONE of the following is the correct IUPAC name of this compound?
A
B
C
D
2,2,4-trimethylpent-2-ene
2,2,2-trimethylpent-3-ene
2,4,4-trimethylpent-2-ene
2,4,4-trimethylpent-3-ene
(2)
1.3
Which one of the following compounds belongs to the same homologous series as
C3H8?
A
B
C
D
C2H2
C3H6
C3H4
C4H10
(2)
1.4
Bromine water would be most likely decolourised by using the gas
A
B
C
D
CH4
C2H6
C3H6
C4H10
(2)
1.5
Consider the organic compound represented below.
The compound is …
A
B
C
D
saturated and branched
unsaturated and branched
saturated and straight-chained
unsaturated and straight-chained
(2)
1.6
Consider the flow diagram:
Propene
H2
Pt
Compound X
The IUPAC name for compound X is:
A
B
C
D
propyne
propan-1-ol
propan-2-ol
propane
(2)
1.7
Which ONE of the following organic compounds has the molecular formula
C5H10O2?
A
B
C
D
Ethyl ethanoate
Butyl ethanoate
Ethyl propanoate
Propyl butanoate
(2)
1.8
Sunflower oil undergoes hydrogenation during the manufacturing process of
margarine. During this process, the…
A
B
C
D
the number of double bonds decreases
carbon chains increase in length
number of single bonds decreases
compound becomes less saturated
(2)
1.9
The reaction represented by the equation below takes place in the presence of a
catalyst. What type of reaction is represented by the following equation?
C13H28 (l) 
A
B
C
D
C2H4 (g) + C3H6 (g) + C8H18 (l)
addition
cracking
substitution
polymerisation
(2)
1.10
During the dehydration of butan-2-ol, represented below, compound Y forms as one
of the products.
Which ONE of the following is the correct condensed structural formula for
compound Y?
(2)
[TOTAL SECTION A = 20 MARKS]
SECTION B
QUESTION 2 [Start on a new sheet of paper]
2.1
Because of its many uses, ammonia is one of the most highly produced inorganic
chemicals. Ammonia is not only widely used in fertilizing agricultural crops, but also
in the production of many plastics, fibres and explosives.
Nitrogen gas and hydrogen gas are combined, in what is known as the Haber process,
to form ammonia. The balanced reaction equation is shown below.
N2 + 3H2  2NH3
2.1.1
∆H < 0
Draw a rough graph of potential energy versus reaction progress for this
reaction. Indicate clearly on the graph the activation energy, the activated
complex and the heat of the reaction.
(4)
2.1.2
Describe shortly what happened at the point on the graph indicated by
“activated complex”.
(3)
2.1.3
Classify this as an endothermic or exothermic reaction.
(1)
2.2
Heptane (C7H16) is the component in petrol that gives petrol the energy to drive
vehicles. When heptane burns in oxygen, the following unbalanced equation
describes the reaction:
C7H16 + O2  CO2 + H2O
2.2.1
Balance the above equation.
(4)
2.2.2
The following bond energies (in kJ.mol-1) are given:
C-H
O=O
C=O
H–O
C–C
414
499
799
460
347
Calculate ∆H for this reaction.
(4)
[16 marks]
QUESTION 3 [Start on a new sheet of paper]
During respiration in cells, glucose is broken down to form carbon dioxide gas and water
vapour according to the following balanced equation:
C6H12O6 (aq) + 6O2 (g)  6CO2 (g) + 6H2O (g)
In one such reaction 3,60 x 106 molecules of carbon dioxide are produced.
(Avogadro’s number is 6,02 x 1023 mol-1)
3.1
Calculate the number of moles of C6H12O6 that were broken down.
3.2
Calculate the volume of CO2 produced; assume that the reaction occurs at
standard temperature and pressure.
(4)
(3)
[7 marks]
QUESTION 4 [Start on a new sheet of paper]
The letters A to F in the table below represent six organic compounds.
A
CH
CH2
CH2
C
CH3
B
CH3CH2CH2CHCH3
|
OH
D
Pentanoic acid
CH3
C
CH2
C
CH2
CH3
H
E
H
H
H
O
C
C
C
C
H H
C
H H
O
H
F
CH3
CH2
O
C
CH2
CH3
H
4.1
Write down the letter(s) that represent each of the following:
(A compound may be used more than once).
4.1.1
An alkyne
4.1.2
Two compounds that are structural isomers
4.1.3
A compound containing a carboxyl group
4.1.4
An aldehyde
4.1.5
An alcohol
(1)
(2)
(1)
(1)
(1)
4.2
4.3
Write down the:
4.2.1
IUPAC name of compound C
(2)
4.2.2
Structural formula of compound D
(2)
Compound F is prepared in the laboratory.
4.3.1
How can one quickly establish whether compound F is indeed being formed
without performing a chemical test?
(1)
4.3.2
4.3.3
Write down the IUPAC name of the alcohol needed to prepare compound F.
(2)
Write down the IUPAC name of compound F.
(2)
[15]
QUESTION 5 [Start on a new sheet of paper]
Consider the following sequence of organic reactions and then answer the questions that
follow. Reactions are labelled from A to E whilst molecules are labelled from II to V.
5.1
What is meant by the term “homologous series”?
5.2
Identify the homologous series to which the following molecules belong:
(2)
5.2.1
II
5.2.2
III
5.2.3
IV
(1)
(1)
5.3
5.4
5.5
(1)
Name the reaction types labelled A, C, D and E in the reaction sequence provided.
(4)
Consider reaction B. To form this molecule labelled IV, a reaction takes place
between molecule III and another molecule from a different homologous series.
Name the homologous series to which the other molecule belongs.
(1)
C4H8O2 has two isomers each of which belongs to a different homologous series.
These are known as functional isomers.
5.5.1
Explain what is meant by the term “functional isomer”.
5.5.2
Name the homologous series to which each of these isomers belongs.
(1)
(2)
5.5.3
Which of these isomers would have a higher boiling point? Explain your
answer in no more than 4 lines.
(3)
[16 marks]
QUESTION 6 [Start on a new sheet of paper]
The table below shows the boiling points of four organic compounds, represented by the
letters A to D, of comparable molecular mass.
6.1
Compound A is used as fuel.
6.1.1
6.1.2
6.1.3
6.1.4
Is compound A in the GAS, LIQUID, or SOLID phase at 25◦C?
(2)
a)
How will the boiling point of an ISOMER of compound A compare to
that of compound A? Write down HIGHER THAN, LOWER THAN
or EQUAL TO.
(2)
b)
Explain your answer to 6.1.2 (a) in no more than three lines.
(3)
Using molecular formulae, write down the balanced equation for the
combustion of compound A in excess oxygen.
(3)
Compound A has a lower boiling point than compound B. Give reasons (in no
more than two lines) for this difference in boiling points by referring to the
following:


Structural difference between the two compounds
Polarity
(2)
6.2
Consider the boiling points of compounds C and D.
6.2.1
6.2.2
Give a reason (in no more than three lines) for this difference in boiling points
by referring to the intermolecular forces present in EACH of these
compounds.
(2)
Which ONE of compounds C or D has a higher vapour pressure? Refer to
their boiling points to give a reason for the answer.
(2)
[16 marks]
QUESTION 7 [Start on a new sheet of paper]
Polyethene, often referred to as polyethylene, is a cheap but very useful plastic.
7.1
7.2
7.3
7.4
Give the molecular formula for the monomer that is used to form polyethene.
(1)
Show, using structural formulae, the formation of polyethene from two monomers.
Your answer should include three separate steps.
(6)
Name the type of polymerisation reaction that takes place in 7.2.
(1)
Give two industrial uses of polyethene.
(2)
[10 marks]
[TOTAL SECTION B = 80 MARKS]