Centre Number
Candidate Number
Candidate Name
CAMBRIDGE INTERNA INTERNATIONAL TIONAL EXAMINA EXAMINATIONS TIONS General Certificate of Education Ordinary Level
5070/2
CHEMISTRY PAPER 2 Theory
MAY/JUNE SESSION 2002 1 hour 30 minutes
Additional materials: Answer paper
TIME
1 hour 30 minutes
INSTRUCTIONS TO CANDIDATES Write your name, Centre number and candidate number in the spaces at the top of this page and on any separate answer paper used. Sections A Answer all questions. Write your answers in the spaces provided on the question paper. pa per. Section B Answer any three questions. Write your answers on the separate answer paper. At the end of the examination, fasten any separate answer paper used securely to the question paper. INFORMATION FOR CANDIDATES The number of marks is given given in brackets [ ] at the end of each question or part question. A copy of the Periodic Table Table is printed on page 16. FOR EXAMINER’S USE Section A B6 B7 B8 B9 TOTAL
This question paper consists of 14 printed pages and 2 blank pages. SJF2132/PW S09666/4 © CIE 2002 2002
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2
For Examiner’s Use
Section A Answer all the questions in this section in the spaces provided. The total mark for this section is 45. A1 Choose from the following solutions to answer the questions below. CuSO4(aq)
KCl (aq)
K2Cr2O7(aq)
KI(aq)
KMnO4(aq)
MgSO4(aq)
NH3(aq)
ZnSO4(aq)
Each solution can be used once, more than once, or not at all. Write the formula for a solution which (a) is alkaline, ................................................................. ................................ ................................................................... .................................................................... .................................. [1] (b) has an orange colour, ................................................................. ................................ ................................................................... .................................................................... .................................. [1] (c) is used to test for an oxidising agent, ................................................................. ................................ ................................................................... .................................................................... .................................. [1] (d) reacts with iron powder to give a pink-brown solid, ................................................................. ................................ ................................................................... .................................................................... .................................. [1] (e) can be used to test for sulphur dioxide, ................................................................. ................................ ................................................................... .................................................................... .................................. [1] (f)
reacts with acidified lead(II) nitrate to give a yellow precipitate. ................................................................. ................................ ................................................................... .................................................................... .................................. [1]
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3
For Examiner’s Use
A2 Hydrogen reacts with chlorine to make hydrogen chloride. The reaction is exothermic. The reaction can be represented by the equation below. H –– H + Cl –– Cl
→
H –– Cl + H –– Cl
∆H =
–184 kJ/ kJ/mol mol
(a) A mixture mixture of 2.5 g of hydrogen hydrogen and 142 g of chlorine is allowed allowed to react. react. (i)
Which gas, hydrogen or chlorine, is in excess? Explain your answer. .................................................................................................................................. .................................................................................................................................. .................................................................................................................................. ..................................................................................................................................
(ii)
Calculate the energy released when 2.5 g of hydrogen reacts completely with chlorine gas.
[3] (b) Explain why the reaction is exothermic, in terms of the energy changes that take place during bond breaking and bond making. .......................................................................................................................................... .......................................................................................................................................... .......................................................................................................................................... ................................................................. ............................... ................................................................... .................................................................... ................................... [3]
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For Examiner’s Use
(c) Draw a ‘dot and cross’ diagram to show the bonding in hydrogen chloride. You only need to draw the outer (valence) electrons of chlorine.
[2] (d) Nitrogen reacts with oxygen to form nitrogen(II) oxide. The energy profile diagram for the reaction is shown below.
2NO(g) energy N2 (g) + O2(g)
progress of reaction (i)
Is the reaction exothermic or endothermic? Explain your answer answer.. .................................................................................................................................. ..................................................................................................................................
(ii)
Label on the diagram the activation energy for the reaction. [2]
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5
For Examiner’s Use
A3 (a) Complete the following table about atmospheric pollutants. atmospheric pollutant
source of pollutant
effect of pollutant
carbon dioxide
complete combustion of fossil fuels
greenhouse effect
carbon monoxide
poisonous
methane
sulphur dioxide [5]
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6 (b) The graph below shows the concentrations of some atmospheric pollutants in a city over a twenty-four hour period.
0.5
unburnt hydrocarbons
0.4
0.3 oxides of nitrogen
concentration/ ppm 0.2
0.1 ozone
0
12 midnight
(i)
4 am
8 am
12 noon
4 pm
8 pm
12 midnight
What is the maximum concentration, in ppm, of unburnt hydrocarbons? ..................................................................................................................................
(ii)
Suggest the source of the unburnt hydrocarbons. ..................................................................................................................................
(iii)
At what time of day is the concentration of ozone highest? ..................................................................................................................................
(iv)
Ozone in the lower atmosphere is a pollutant. State one effect of ozone in the lower atmosphere. .................................................................................................................................. [4]
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For Examiner’s Use
7
For Examiner’s Use
(c) Ozone also occurs in the upper atmosphere. (i)
Why is ozone in the upper atmosphere important? ..................................................................................................................................
(ii)
State one type of compound that is responsible for ozone depletion. .................................................................................................................................. [2]
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8 A4 Antacid tablets neutralise acids. A student investigated the time taken for an antacid tablet to react completely completely with with excess excess hydroch hydrochloric loric acid acid (the reaction reaction time) time) under different different conditions. The table shows the results. experiment number
volume of aciid / cm3 ac
concentration of acid aci d in in mol mol / dm3
temperature of acid / °C
reaction time / seconds
1
50
1.0
25
132
2
50
2.0
25
65
3
100
2.0
25
65
4
50
2.0
35
33
(a) Which two experiments show that the volume of acid used does not affect the rate of reaction? …………………… and ……………………
[1]
(b) Describe and explain the effect of increasing the temperature on the rate of reaction, in terms of collisions between reacting particles. .......................................................................................................................................... .......................................................................................................................................... ................................................................. ................................ ................................................................... .................................................................... .................................. [2] (c) The antacid tablet contains calcium carbonate. (i)
Write down the equation for the reaction between calcium carbonate and hydrochloric acid. ..................................................................................................................................
(ii)
Calculate the number of moles of hydrochloric acid used in experiment 2.
(iii)
Calculate the mass of calcium carbonate that will react with this number of moles of hydrochloric acid.
Mass of calcium carbonate. …………………… [4] 5070/2 Jun02
For Examiner’s Use
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For Examiner’s Use
A5 The structures of three organic molecules are shown below.
H
H
C
H
C
H
H
ethene
H
H
C
C
H
H
H O
H
H
C H
ethanol
O
H
C O
ethanoic acid
(a) Describe an industrial process to make ethanol from ethene. .......................................................................................................................................... .......................................................................................................................................... ................................................................. ............................... ................................................................... .................................................................... ................................... [3] (b) Name a reagent that can be used to convert ethanol into ethanoic acid. ................................................................. ............................... ................................................................... .................................................................... ................................... [1] (c) Ethanol and concentrated ethanoic acid react to form the ester ethyl ethanoate. (i)
Name the other product formed. ..................................................................................................................................
(ii)
Name the catalyst used in this reaction. ..................................................................................................................................
(iii)
The reaction between ethanol and ethanoic acid can reach dynamic equilibrium. What is meant by the term dynamic equilibrium ? .................................................................................................................................. .................................................................................................................................. .................................................................................................................................. ............................................................... .............................. ................................................................... .............................................................. ............................ [4]
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10 (d) Ethanoic acid is a weak acid. It reacts with magnesium giving a gas and a magnesium salt. (i)
What is meant by the term weak acid ? .................................................................................................................................. .................................................................................................................................. ..................................................................................................................................
(ii)
Name the gas formed. ..................................................................................................................................
(iii)
What is the formula of the magnesium salt formed? ................................................................ .............................. ................................................................... ............................................................. ............................ [3]
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For Examiner’s Use
11 Section B Answer three questions from this section. The total mark for this section is 30.
B6 Sodium chloride is used in making many important chemicals including chlorine and hydrogen. (a) Write the electrode reactions for the electrolysis of molten sodium chloride. Which electrode reaction is an oxidation? Explain your answer.
[ 3]
(b) Explain why the electrolysis of aqueous sodium chloride using inert electrodes gives hydrogen. [1] (c) Explain the three stages in the purification of water supplies.
[3]
(d) Hydrogen is used to manufacture ammonia, NH3. Calculate the volume of hydrogen needed to react completely completely with with 240 dm3 of nitrogen, all gas volumes measured at room temperature and pressure. [3]
B7 Nitrogenous fertilisers are used to increase crop yield. Potassium nitrate, KNO3, and ammonium sulphate, (NH4)2SO4, are two nitrogenous fertilisers. (a) Which fertiliser, potassium nitrate or ammonium sulphate contains the greater percentage mass of nitrogen? Explain your answer. [3] (b) Explain some of the pollution problems that can be caused by the over-use of nitrogenous fer tilisers. [3] (c) Explain why adding calcium hydroxide to a soil can cause a loss of nitrogen.
[2]
(d) A water supply is contaminated with ammonium sulphate. Describe a chemical test for the sulphate ion in the water.
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[2]
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12 B8 The table shows the energy released when one gram of an alkane or an alkene is completely burned. molecular formula
Energy released per gram / kJ
CH4
55.6
C2H4
50.3
C4H8
42.5
C4H10
49.6
C20H42
47.2
(a) Draw two possible structures for the compound with molecular formula C4H8.
[2]
(b) Explain how you can tell that C20H42 is an alkane.
[1]
(c) Select data from the table to show how the energy released per gram varies with the number of carbon atoms in one molecule of an alkane alkane.. [1] (d) Write the equation for the complete combustion of C4H8.
[2]
(e) A sample of a hydrocarbon hydrocarbon contains contains 0.240 g of carbon and 0.050 g of hydrogen.
(f)
(i)
Calculate the empirical formula of this hydrocarbon.
(ii)
The hydrocarbon is one of the compounds in the table. Which one?
State a reagent used to distinguish between an alkane and an alkene.
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[3] [1]
13 B9 The Periodic Table Table is arranged in groups. (a) Rubidium, Rb, is in Group I of the Periodic Table. It reacts with water according to the equation below b elow.. 2Rb(s) + 2H2O(l)
→
2RbOH(aq) + H2(g)
Predict what you would see wh whe en a small piece of ru rub bidi dium um is adde ded d to cold wat ate er.
[3]] [3
(b) Chlorine is in Group VII of the Periodic Table. Table. Chlorine, Cl2, reacts with aqueous sodium bromide. (i)
Predict what you would see in this reaction.
(ii)
Write a balanced ionic equation for this reaction. [2]
(c) Lithium reacts with fluorine to form lithium fluoride. (i)
Draw a ‘dot and cross’ diagram to show the bonding in lithium fluoride. You should show all the th e electrons.
(ii)
Explain why lithium fluoride conducts electricity when molten but not as a solid.
(iii)
State on one e ot othe herr physical property of lithium fluoride. [5]
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