Cambridge IGCSE Chemistry - 0620 - Supplement Paper 4 2016 Winter Zone 1

The table gives some information about five substances.

[Table_1]

(a) Which substance in the table has ionic bonding?
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(b) Which substance in the table has a giant covalent structure?
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(c) Name a method you could use to separate a mixture of substance J and water.
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(d) Name a method you could use to obtain substance F from a mixture of substance F and water.
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(e) Describe how you could obtain a solid sample of substance H from a mixture of substance H and substance G.
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(f) Substance J is a metal.
Describe how substance J is able to conduct electricity when it is a solid.
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Matter can exist as solid, liquid or gas. The arrows show some changes of state.



(a) Name the changes of state represented on the diagram.

(i) A ......................................................................................................... [1]

(ii) B ......................................................................................................... [1]

(iii) C ......................................................................................................... [1]

(b) Explain why energy has to be supplied to turn a liquid into a gas.

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(c) The diagrams represent the same number of particles of a gas in two containers, D and E, which have different volumes. The two containers are at the same temperature.



In which container will the pressure be higher? Explain your answer.

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(a) Petroleum is a mixture of hydrocarbons. It is separated into useful fractions by fractional distillation. This can be done using the fractionating column shown.

(i) What happens to the petroleum at point X, before it enters the fractionating column?
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(ii) State two ways in which fraction O differs from fraction L.
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(b) Most of the hydrocarbons obtained from petroleum are alkanes. The alkanes are an homologous series of saturated hydrocarbons with the general formula $C_nH_{2n+2}$.
Give two characteristics, other than having the same general formula, of members of an homologous series.
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(c) The alkane with the molecular formula $C_5H_{12}$ can exist as a number of structural isomers.
Draw the structures of two isomers with the formula $C_5H_{12}$.
[2]
(d) The alkane ethane has the structure shown.

When a mixture of ethane and chlorine is exposed to ultraviolet light a substitution reaction takes place.
Draw the structure of one organic product from this substitution reaction.
[1]

(e) Isoprene is a naturally occurring hydrocarbon.
(i) Explain how the name of isoprene suggests that it contains a $C=C$ double bond.
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(ii) A sample of isoprene had the following composition by mass: C, 88.24%; H, 11.76%.
Calculate the empirical formula of isoprene. Show all your working.
empirical formula = ............................... [3]
(iii) What additional information would be required to calculate the molecular formula of isoprene?
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(a) Ammonia, $NH_3$, is made by reacting nitrogen with hydrogen in the Haber process.
(i) Write a chemical equation for the formation of ammonia in the Haber process.
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(ii) Name the raw materials from which nitrogen and hydrogen are obtained.
nitrogen ...........................................................................................................................
hydrogen ......................................................................................................................... [2]
(iii) State the temperature and pressure used in the Haber process. Include the units.
temperature ...................................................................................................................
pressure ........................................................................................................................... [2]

(b) Ammonia is also made when ammonium carbonate decomposes.
$(NH_4)_2CO_3(s) \rightleftharpoons 2NH_3(g) + H_2O(g) + CO_2(g)$
The reaction is reversible and can reach a position of equilibrium.
The graph shows how the yield of ammonia at equilibrium changes with temperature and pressure.

(i) What is meant by the term \textit{equilibrium} for a reversible reaction?
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(ii) Using information from the graph, explain whether the reaction is endothermic or exothermic.
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(iii) State and explain the effect of increasing the pressure on the yield of ammonia in this reaction.
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Copper(II) sulfate solution was electrolysed using the apparatus shown.


(a) A gas was formed at the anode.
Identify this gas and give the test for this gas.
gas ...............................................................................................................
test ...............................................................................................................
result of test .................................................................................................

(b) During electrolysis, electricity passes through the copper(II) sulfate solution.
Solid copper(II) sulfate does not conduct electricity.
Explain both of these statements.
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(c) The electrolysis was repeated using copper electrodes in place of carbon electrodes. The ionic half-equations for the reactions at the two electrodes are shown.
anode $\text{Cu(s)} \rightarrow \text{Cu}^{2+}(\text{aq}) + 2\text{e}^-$
cathode $\text{Cu}^{2+}(\text{aq}) + 2\text{e}^- \rightarrow \text{Cu(s)}$

(i) Which species is reduced during the electrolysis? Explain your answer.
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(ii) The masses of the copper electrodes changed during the electrolysis.
State how and explain why the masses of the two copper electrodes changed.
Use the ionic half-equations to help you.
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(iii) Explain why, during the electrolysis, the colour of the copper(II) sulfate solution does not change.
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Nylon, Terylene and proteins are all polymers.

(a) What is a polymer?
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(b) Proteins are natural polymers. Proteins are biodegradable.

(i) Name the type of linkage in proteins.
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(ii) What is meant by the term biodegradable?
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(iii) Name another natural polymer.
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(c) Nylon and Terylene are synthetic polymers.
The repeat unit of nylon can be shown as


Terylene can be made from the monomers shown.


Draw a diagram to show the repeat unit of Terylene. [3]

Calcium chloride can be made by reacting calcium carbonate with hydrochloric acid.

$\text{CaCO}_3(s) + 2\text{HCl}(aq) \rightarrow \text{CaCl}_2(aq) + \text{H}_2\text{O}(l) + \text{CO}_2(g)$

An excess of calcium carbonate was added to 50.0 cm$^3$ of 0.500 mol/dm$^3$ hydrochloric acid. The solution was filtered to remove the excess calcium carbonate.

(a) How many moles of HCl were used in this reaction?

......................................... mol [2]

(b) Deduce the number of moles of carbon dioxide gas made in this reaction.

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(c) Calculate the mass of carbon dioxide made in this reaction.

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(d) Calculate the volume, in dm$^3$, of carbon dioxide made in this reaction at room temperature and pressure (r.t.p.).

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Magnesium carbonate reacts with dilute hydrochloric acid.

$\text{MgCO}_3(s) + 2\text{HCl}(aq) \rightarrow \text{MgCl}_2(aq) + \text{H}_2\text{O}(l) + \text{CO}_2(g)$

An excess of magnesium carbonate pieces was added to dilute hydrochloric acid. The apparatus in the diagram was used to measure the volume of gas produced. The total volume of gas collected was recorded every 20 seconds.



(a) The results obtained are shown on the graph.



(i) Describe how the rate of this reaction changed during the reaction. Explain why the rate changed in this way.
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(ii) The experiment was repeated using the same mass of powdered magnesium carbonate with the same volume and concentration of dilute hydrochloric acid.
Explain how the initial rate of reaction and total volume of gas collected would compare to the first experiment.
initial rate of reaction .........................................................................................................................
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total volume of gas ..............................................................................................................................
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(b) A piece of magnesium ribbon was cleaned. The experiment was repeated using this clean magnesium ribbon instead of magnesium carbonate.

$\text{Mg}(s) + 2\text{HCl}(aq) \rightarrow \text{MgCl}_2(aq) + \text{H}_2(g)$

This reaction is exothermic. The rate of the reaction gradually increased over the first 2 minutes.
Explain why the rate of the reaction increased.
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