BOTSWANA EXAMINATIONS COUNCI L

Botswana General Certificate of Secondary Education

CANDIDATE
NAME

GENTRE CANDIDATE
NUMBER NUMBER

-.G
6:
CHEMI$TRY 0570/03
E- Paper 3 October/November 2014
6!:
-I I hour 15 minutes
-.-
Candidates answer on the'Question Paper.
&G-
---
^- No Additional Materials are required.
.G
''- READ THESE INSTRUCTIONS FIR$T

Write your Centre number, candidate number and name in the spaces provided at the top of this page.
Write in dark blue or black pen.
You may use a soft pencil for any diagrams, graphs or rough working.
Do not use staples, paper clips, highlighters, glue or correction fluid.

Answer all questions.

Write your answers in the spaces provided on the question paper.
Show your working for any calculations,
You may use a calculator
The number of marks is given in brackets [] at the end of each question or part question.

A copy of the Periodic Table is printed on page 12.

For Examiner's Use

Total

This document consists of 12 printed pages.

o BEC 2014 [Turn over

 -l

For
2
Examlia/s
Use
1 Each box below contains a definition of a term. Join each box to the correct term.
One has been done for you.

term

The breaking down of a substance by reaction deliquescent

with water.

The loss of electrons from a molecule or ion. hygroscopic

A substance that absorbs water vapour exothermic

from the air and dissolves in it.

A substance that absorbs water vapour hydrolysis

from the air but does not dissolve in it.

The reprocessing of waste materials to form new oxidation

substances.

A chemical reaction that loses heat energy. recycllng

flotal:5]
 For
3 Examiner's
Use

2 A substance used to clean false teeth contains potassium percarbonate, K2C2O6.

(a) How many atoms are present in potassium percarbon?t€, KeCzOs?

t1l

(b) Potassium percarbonate is an ionic compound containing two ions.

(i) Write the formulae of the two ions.

......... and l2l
(ii) Suggest two physical properties of potassium percarbonate.

.................. t2l

(c) Calculate the relative molecular mass of pota$sium percarbonate, K2C2O5.

I1I

(d) Calculate the percentage by mass of carbon in potassium percarbonate.

l1I

(e) When potassium percarbonate, KzezOo, is strongly heated, it decomposes completely

into potassium carbonate, carbon dioxide and oxygen.

Write a balanced chemical equation for the reaction.

............ . .. ..t21

fiotal: 9]

o BEC 2014 0570/03/o/N/14 [Turn over

 ', 4 For
Examin,
lJse
3 Sulphuric acid is manufactured industrially from sulphur by the Contact Process.

(a) Give one source of sulphur.

t1I

(b) Name the catalyst used in the Contact Process.

l1l

(c) Outline the steps involved in the manufacture of sulphuric acid from sulphur including
the Contact Process. You may write equations.

.............".... t4t

(d) Give one use of sulphuric acid.

........"........ tl I
 For
5 Examiner's
Use
(e) Dilute sulphuric acid was reacted with powdered limestone, CaCO3, and the volume of
carbon dioxide produced was collected and measured. The table shows the results.

time/s 0 10 20 30 40 50 60 70 80
volume of carbon dioxide / cm3 0 60 90 105 '112 118 120 120 124

(i) Plot a graph of volume of carbon dioxide produced (vertical axis) against time.

l3I

A ntr^ tn4 ,
 For
.. 6 Examlner's
Use
(ii) Suggest a reason why the volume of carbon'dioxide reached a maximum value.

tll
(iii) Describe a positive test for carbon dioxide.

test... '...'.......... tll

result -...'.."....' t1l

(iv) Name the type of reaction that occurs between sulphuric acid and limestone.

I1l

(f) The carbon dioxide gas collected was dissolved in water to form carbonic acid, HzCOs,
which is a weak acid.

(i) What is meant by the term weak acid?

t1t

(ii) Suggest the pH of carbonic acid.

t1l

(iii) Give another example of a weak acid.

t1t

flotal: 17]
 \
For
7 Examinels
Use

4 Methane and steam will react together at high temperatures and in the presence of a catalyst.
The reaction is reversible. The equation for the reaction is as shown.

CHa(g) + HzO(g) * CO(g) + 3Hz(g) AH = +210 kJ/mol

(a) What is meant by a reversible reaction?

t1l

(b) ln a closed container, the reaction proceeds until it reaches a state of equilibrium.

What happens to the rate of the forward and backward reactions at equilibrium?

11l

(c) What will be the effect on the amount of hydrogen ga$, H2, at equilibrium if;

(i) the pressure in the container is increased,

t1t

(ii) the temperature of the mixture is increased,

t1l

(iii) some of the carbon monoxide is removed from the equilibrium mixture?

I1I

(d) Draw a labelled energy level diagram, including activation energy, for the backward
reaction.

t4I

lTotal: 9l

o BEC 2014 0570/03/o/N/14 [Turn over

 I For
Examiner's
5 A large tank of liquid industrial waste contains a mixture of sulphuric acid
and ammonium
Use

nitrate.

(a) Name two cations present in the mixture.

and ..
t2t
(b) Describe a chemicaltest to confirm the presence of sulphate ions in the tank.

.................. t2I

(c) A 10.0 cm3 sample of the mixture from the tank is diluted with water to prepare 250 cm3
of solution. ln a titration, 25.0cm3 of the diluted solution of the mixture
reacts completely
with 20.0cm3 of 0'2mol/dm3 sodium hydroxide. The equation for the reaction
is as shown.

HzSOa(aq) + 2NaOH(aa) --+ NazSon(aq) + 2HzO(l)

(i) Calculate the number of moles of sodium hydroxide contained in 20.0
cm3 of
0.2 molidms solution.

Izt
(ii) Use your answer to {c}(i) to calculate the number of moles of sulphuric
acid contained
in 25.0 cm3 of the diluted solution.

t1l
(iii) Calculate the number of moles of sulphur"ic acid contained in 250 cm3 of the diluted
solution.

tzt
 For
I Examiner's
Use

(iv) State the number of moles of sulphuric acid contained in the 10.0cm3 sample from
the tank.

t1l

(v) Calculate the concentration measured in mol/dm3 of sulphuric acid in the tank.

l2l
(vi) The tank contained 20dm3 of the liquid industrial waste.
Calculate the mass of sulphuric acid in the mixture in the tank.
(M,[HzSOr] = 98)

t2t

[Total: 14]
 10 For
Examiner's
Use
6 The table shows information about compounds of the same homologous series.

molecular melting boiling

name structural formula
formula pointi "C pointi 'C

propane CsHe
'{-Fh' - 190 -42

butane TT T T - 138
"-?-?-?-?-"
HH H H
0

TTTTT
H-C-C-C-C-C-H
CsHrz

II I I I -129

hexane CeHr+ -95 69

(a) Complete the table to show the four missing pieces of information. Wl

(b) Write the name and the general formula of the homologous series of the compounds
in the table.

name t1l

generalformula I1l

(c) Give two characteristics of the homologous series, other than the trend in melting
point and boiling point.

1 .......

2....".... ............t21

(d) ln what state is butane at room temperature and pressure?

.J.............r.. ......t1l
 -'l
l

For
11 Examiner's
Use

(e) Draw the structural formulae of two isomers of CsHrz other than that given in the table.

t21

(0 Propane reacts with chlorine gas according to the equation shown.

CsHa(g) + clz(9) --+ C3H7C(g) + Hcl(g)

(i) Name the type of chemical reaction that occurs between propane and chlorine.

t1l

(ii) Draw a 'dot' and 'cross'diagram to show the arrangement of outer electrons in
a molecule of hydrogen chloride, HCI

t2l

(g) Two types of polymerisation are addition and condensation. Explain the difference
between them.

fiotal:16]

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 12
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