Cambridge IGCSE Chemistry - 0620 - Supplement Paper 4 2017 Summer Zone 3

Six different atoms can be represented as follows.
[Image_1: Atoms List]
(a) Answer the following questions using atoms from the list. Each atom may be used once, more than once or not at all.
Select one atom from the six shown which
(i) has exactly seven protons,
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(ii) has exactly six neutrons,
.............................................................................................................. [1]
(iii) has more protons than neutrons,
.............................................................................................................. [1]
(iv) has the electronic structure [2,5],
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(v) is an atom of an element from Group VII of the Periodic Table,
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(vi) is an atom of a noble gas.
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(b) Two of the six atoms shown are isotopes of each other.
(i) What is meant by the term isotopes?
.............................................................................................................. [2]
(ii) Which two of the six atoms shown are isotopes of each other?
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(iii) Why do isotopes have identical chemical properties?
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Cyclopropane is a colourless gas. Cyclopropane reacts with bromine at room temperature. The chemical equation for the reaction is shown.

(a) (i) What is the empirical formula of cyclopropane?
........................................................................................................................ [1]
(ii) What colour change, if any, would you see when cyclopropane is bubbled into aqueous bromine?
initial colour ........................................................
final colour .......................................................... [2]
(b) The reaction of cyclopropane with bromine is exothermic.
(i) Complete the energy level diagram for this reaction by

• adding the product of the reaction,
• labelling the energy change, $ \Delta H $.

Magnesium is a metal.
(a) Describe the structure and bonding in magnesium.
.......................................................................................................................... .......................................................................................................................... .......................................................................................................................... .......................................................................................................................... [3]
(b) Why can magnesium conduct electricity when solid?
.......................................................................................................................... .......................................................................................................................... .......................................................................................................................... .......................................................................................................................... [2]
(c) Why is magnesium malleable?
.......................................................................................................................... .......................................................................................................................... .......................................................................................................................... .......................................................................................................................... [2]
(d) Magnesium reacts with sulfur to form the ionic compound magnesium sulfide, MgS.
The diagrams show the electronic structures of atoms of magnesium and sulfur.

(i) Complete the diagrams to show the electronic structures of the ions in magnesium sulfide. Show the charges on the ions.
[3]
(ii) Ionic compounds, such as magnesium sulfide, do not conduct electricity when solid. Magnesium sulfide does not dissolve in water. Magnesium sulfide does conduct electricity under certain conditions.
State the conditions needed for magnesium sulfide to conduct electricity. Explain why magnesium sulfide conducts electricity under these conditions.
.......................................................................................................................... .......................................................................................................................... .......................................................................................................................... .......................................................................................................................... [2]

Gasoline is used as a fuel for cars. It is a mixture of hydrocarbons.
(a) Name the raw material from which gasoline is obtained.
........................................................................................................................ [1]
(b) One of the compounds in gasoline is heptane, $C_{7}H_{16}$. Heptane is a saturated hydrocarbon.
(i) What is meant by the term saturated hydrocarbon?
saturated ..................................................................................................................
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hydrocarbon ............................................................................................................
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(ii) To which homologous series does heptane belong?
.............................................................................................................................. [1]
(iii) Give two characteristics of an homologous series.
1 .............................................................................................................................
2 ............................................................................................................................. [2]
(iv) Complete the chemical equation for the complete combustion of heptane.
$C_{7}H_{16} + .............O_{2} \rightarrow ....................... + ........................$ [2]
(c) Car engines produce carbon monoxide and oxides of nitrogen.
(i) Name an environmental problem that is caused by the release of oxides of nitrogen into the air.
.............................................................................................................................. [1]
(ii) Explain how carbon monoxide and oxides of nitrogen are formed in car engines.
carbon monoxide ...................................................................................................
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oxides of nitrogen ...................................................................................................
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(iii) State one adverse effect of carbon monoxide on human health.
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(iv) Describe and explain how catalytic converters remove oxides of nitrogen from car engine exhaust fumes. You are advised to include a chemical equation in your answer.
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(d) The formula $C_{4}H_{10}$ represents two structural isomers, A and B.

(i) Name isomer A.
.............................................................................................................................. [1]
(ii) What is meant by the term structural isomers?
..............................................................................................................................
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(iii) Isomer B reacts with chlorine in a substitution reaction.
Give the conditions required for the reaction to occur and draw the structures of two possible products, one of which is organic and one of which is not organic.
conditions ............................................................................................................
structures of products

The diagram shows a simple cell.
The simple cell was used with different metals as electrodes. The voltages were recorded in the table. [Table_1]
- If the voltage measured is positive then metal 2 is more reactive than metal 1.
- If the voltage measured is negative then metal 1 is more reactive than metal 2.

| | metal 2 |
|------------|-------------------------------------------|
| | beryllium | cobalt | nickel | silver | vanadium |
| metal 1 | | | | | |
| beryllium | 0.0V | −1.6V | −1.6V | not measured | −0.7V|
| cobalt | 0.0V | 0.0V | −1.1V | 0.9V | |
| nickel | | 0.0V | −1.1V | 0.9V | |
| silver | | | 0.0V | 2.0V | |
| vanadium | | | | | 0.0V |

- The more reactive metal is oxidised.
- The bigger the difference in reactivity of the metals, the larger the reading on the voltmeter.

(a) In a simple cell using nickel and silver, the nickel is oxidised.
(i) Define oxidation in terms of electrons. [1]
(ii) Nickel forms ions with a charge of +2.
Write an ionic half-equation to show the oxidation of nickel. [1]
(iii) What will happen to the mass of the nickel electrode when the nickel is oxidised? [1]

(b) Use the data in the table to answer the following questions.
(i) Which of the metals in the table is the most reactive? Explain your answer. [2]
(ii) State which two different metals have the same reactivity. [1]
(iii) Predict the voltage produced by a simple cell with beryllium as metal 1 and silver as metal 2. [2]

(c) Describe how the simple cell in the diagram can be used to show that magnesium is more reactive than beryllium. Explain your answer. [2]

Barium carbonate, BaCO$_3$, is an insoluble solid.

(a) When barium carbonate is heated strongly, it undergoes thermal decomposition. One of the products is barium oxide.

(i) Write a chemical equation for the thermal decomposition of barium carbonate.
............................................................................................................................................... [1]

(ii) Suggest the pH of the solution formed when barium oxide is added to water.
............................................................................................................................................... [1]

(iii) Barium nitrate decomposes on heating in the same way as magnesium nitrate decomposes. Name the two gaseous products formed when barium nitrate is heated.
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(b) Aqueous sodium carbonate is added to aqueous barium nitrate.

(i) Write a chemical equation for the reaction of aqueous sodium carbonate with aqueous barium nitrate.
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(ii) Describe how a pure sample of barium carbonate could be obtained from the resulting mixture.
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(c) Barium carbonate reacts with dilute hydrochloric acid.

BaCO$_3$ + 2HCl → BaCl$_2$ + CO$_2$ + H$_2$O

9.85 g of barium carbonate were added to 250 cm$^3$ of 1.00 mol/dm$^3$ hydrochloric acid. This is an excess of hydrochloric acid.

(i) Calculate how many moles of barium carbonate were used in this experiment.
moles of barium carbonate = …………………………… mol [2]

(ii) Deduce how many moles of carbon dioxide were made when all the barium carbonate had reacted.
moles of carbon dioxide = …………………………… mol [1]

(iii) Calculate the volume of carbon dioxide formed in (c)(ii) at room temperature and pressure, in dm$^3$.
volume of carbon dioxide = …………………………… dm$^3$ [1]

(iv) Calculate how many moles of hydrochloric acid there were in excess.
excess moles of hydrochloric acid = …………………………… mol [2]