Cambridge IGCSE Chemistry - 0620 - Supplement Paper 4 2015 Summer Zone 1

(a) Coal is a solid fossil fuel.

Name two other fossil fuels.

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(b) Two of the elements present in a sample of coal are carbon and sulfur.

A sample of coal was heated in the absence of air and the products included water, ammonia and hydrocarbons.

Name three other elements present in this sample of coal.

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(c) Sulfur, present in coal, is one major cause of acid rain. Sulfur burns to form sulfur dioxide which reacts with rain water to form sulfuric acid.
(i) Describe how the high temperatures in vehicle engines are another cause of acid rain.

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(ii) Give two harmful effects of acid rain.

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(d) In 2010, a large coal-burning power station in the UK was converted to burn both coal and wood.

Explain why the combustion of wood rather than coal can reduce the effect of the emissions from this power station on the level of carbon dioxide in the atmosphere.

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(a) Explain how the addition of oxygen and calcium oxide removes these impurities. Include an equation for a reaction of oxygen and a word equation for a reaction of calcium oxide in this process.
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(b) Mild steel is the most common form of steel. Mild steel contains a maximum of 0.3% of carbon.
High carbon steel contains 2% of carbon. It is less malleable and much harder than mild steel.
(i) Give a use of mild steel. [1]
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(ii) Suggest a use of high carbon steel. [1]
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(iii) Explain why metals are malleable. [3]
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(iv) Suggest an explanation why high carbon steel is less malleable and harder than mild steel. [2]
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(a) The reactions between metals and acids are redox reactions.

$Zn + 2H^+ \rightarrow Zn^{2+} + H_2$

(i) Which change in the above reaction is oxidation, Zn to $Zn^{2+}$ or $2H^+$ to $H_2$? Give a reason for your choice.
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(ii) Which reactant in the above reaction is the oxidising agent? Give a reason for your choice.
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(b) The rate of reaction between a metal and an acid can be investigated using the apparatus shown below.



A piece of zinc foil was added to 50 $cm^3$ of hydrochloric acid, of concentration $2.0\,mol/dm^3$. The acid was in excess. The hydrogen evolved was collected in the gas syringe and its volume measured every minute. The results were plotted and labelled as graph 1.

The experiment was repeated to show that the reaction between zinc metal and hydrochloric acid is catalysed by copper. A small volume of aqueous copper(II) chloride was added to the acid before the zinc was added. The results of this experiment were plotted on the same grid and labelled as graph 2.

(i) Explain why the reaction mixture in the second experiment contains copper metal. Include an equation in your explanation.
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(ii) Explain how graph 2 shows that copper catalyses the reaction.
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(c) If the first experiment was repeated using ethanoic acid, $CH_3COOH$, instead of hydrochloric acid, how and why would the graph be different from graph 1?
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(d) Calculate the maximum mass of zinc which will react with 50 $cm^3$ of hydrochloric acid, of concentration $2.0\,mol/dm^3$.

$Zn + 2HCl \rightarrow ZnCl_2 + H_2$

Show your working.

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The alcohols form a homologous series.
(a) (i) Give three characteristics which all members of a homologous series share.
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(ii) Give the name of the third member of this series.
name ........................................
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(iii) Deduce the molecular formula of the alcohol whose $M_r = 158$. Show your working.
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(b) Explain why the following two alcohols are isomers.

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(c) This question is based on typical reactions of butan-1-ol.
(i) When butan-1-ol, $CH_3CH_2CH_2CH_2OH$, is passed over the catalyst silicon(IV) oxide, water is lost.
Dedupe the name and the structural formula of the organic product in this reaction.
name ........................................
structural formula
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(ii) Suggest the name of the ester formed from butanol and ethanoic acid.
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(iii) Butan-1-ol is oxidised by acidified potassium manganate(VII).
Deduce the name and the structural formula of the organic product in this reaction.
name ........................................
structural formula
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The halogens are a group of non-metals in Group VII of the Periodic Table.
(a) The reactivity of the halogens decreases down the group.
Describe an experiment which shows that chlorine is more reactive than iodine. Include an equation in your answer.

(b) The halogens form interhalogen compounds. These are compounds which contain two different halogens.
Deduce the formula of the compound which has the composition 0.013 moles of iodine atoms and 0.065 moles of fluorine atoms.

(c) Iodine reacts with chlorine to form a dark brown liquid, iodine monochloride.

When more chlorine is added and the tube is sealed, a reversible reaction occurs and the reaction comes to equilibrium.
Give another example of a reversible reaction.
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Explain the term equilibrium.
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(d) Chlorine is removed from the tube and a new equilibrium is formed.
Explain why there is less of the yellow solid and more dark brown liquid in the new equilibrium mixture.

(e) A sealed tube containing the equilibrium mixture is placed in ice-cold water. There is an increase in the amount of yellow solid in the equilibrium mixture.
What can you deduce about the forward reaction in this equilibrium?

Explain your deduction.

Acid-base reactions are examples of proton transfer.
(a) Ethylamine is a weak base and sodium hydroxide is a strong base.
(i) In terms of proton transfer, explain what is meant by the term weak base.
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(ii) Given aqueous solutions of both bases, describe how you could show that sodium hydroxide is the stronger base. How could you ensure a 'fair' comparison between the two solutions?
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(b) Ethylamine reacts with acids to form salts.
\[\text{CH}_3\text{CH}_2\text{NH}_2 + \text{HCl} \rightarrow \text{CH}_3\text{CH}_2\text{NH}_3\text{Cl}\]
ethylammonium chloride
(i) Complete the equation for the reaction between sulfuric acid and ethylamine. Name the salt formed.
......\text{CH}_3\text{CH}_2\text{NH}_2 + ........... \rightarrow ..........................
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(ii) Amines and their salts have similar chemical properties to ammonia and ammonium salts. Suggest a reagent that could be used to displace the weak base, ethylamine, from its salt ethylammonium chloride.
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(c) Gases diffuse, which means that they move to occupy the total available volume.
(i) Explain, using kinetic particle theory, why gases diffuse.
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(ii) When the colourless gases hydrogen bromide and ethylamine come into contact, a white solid is formed.
\[\text{CH}_3\text{CH}_2\text{NH}_2(g) + \text{HBr}(g) \rightarrow \text{CH}_3\text{CH}_2\text{NH}_3\text{Br(s)}\]
white solid
The following apparatus can be used to compare the rates of diffusion of the two gases ethylamine and hydrogen bromide.
Predict at which position, A, B or C, the white solid will form. Explain your choice.
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