Cambridge IGCSE Chemistry - 0620 - Core Paper 3 2016 Summer Zone 2

(a) Answer the following questions about these substances.
(i) Which two of these substances are ionic?
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(ii) Which one of these substances is an element?
Explain your answer.
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(iii) Determine the simplest formula for substance D.
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(b) Phosphorus has one naturally occurring isotope.
(i) Determine the number of neutrons present in one atom of the isotope $^{31}_{15}P$.
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(ii) How many electrons are there in the outer shell of one phosphorus atom?
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(iii) Determine the total number of electrons present in a phosphorus molecule, $P_4$.
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(c) What type of oxide is phosphorus(V) oxide?
Explain your answer.
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(a) The table describes the ease of reduction of some metal oxides with carbon.

\[ \begin{array}{|c|c|} \hline \text{metal oxide} & \text{ease of reduction on heating} \\ \hline \text{lead oxide} & \text{moderate heating at 200 °C needed} \\ \text{nickel oxide} & \text{high temperature at 750 °C needed} \\ \text{titanium oxide} & \text{very high temperatures above 1700 °C needed} \\ \text{zinc oxide} & \text{very high temperature at 900 °C needed} \\ \hline \end{array} \]

Put the metals in order of their reactivity. Put the least reactive metal first.

[2]

(b) Aluminium is extracted by the electrolysis of molten aluminium oxide.

Predict the products of this electrolysis at the
positive electrode (anode), ..........................................................
negative electrode (cathode) ..........................................................
[2]

(c) When iron reacts with dilute hydrochloric acid, an aqueous solution containing iron(II) ions is formed.

Describe a test for iron(II) ions.
test ..........................................................
result ..........................................................
[2]

(d) Iron rusts very easily.

(i) Complete the following sentence.
Iron rusts in the presence of ___________________ and ___________________.
[2]

(ii) Describe one method of rust prevention and explain how it works.
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[2]

Sulfur dioxide reacts with excess oxygen to form sulfur trioxide.

$2SO_2(g) + O_2(g) ightleftharpoons 2SO_3(g)$

(a) What is the meaning of the symbol $\rightleftharpoons$?
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(b) The energy level diagram for the reaction is shown.



Is this reaction exothermic or endothermic?
Give a reason for your answer.
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(c) The graph shows how the percentage yield of sulfur trioxide changes with temperature when the pressure is kept constant.



(i) Describe how the percentage yield of sulfur trioxide changes with temperature.
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(ii) Determine the percentage yield of sulfur trioxide when the temperature is 500 °C.
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(d) Describe a test for sulfur dioxide.
test .................................................................................................................................
result ................................................................................................................................. [2]

(e) Give one use of sulfur dioxide.
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(f) Sulfur dioxide reacts with magnesium.

$2Mg + SO_2 ightarrow 2MgO + S$

Which substance is reduced in this reaction?
Explain your answer.
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(g) Sulfur dioxide reacts with water to form sulfurous acid, $H_2SO_3$. Sulfurous acid reacts with hydrogen sulfide to form water and sulfur.
Complete the chemical equation for this reaction.

$H_2SO_3 + 2H_2S ightarrow .....H_2O + 3S$
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Alkanes, alkenes and alcohols are three different homologous series of organic compounds.

(a) What is meant by the term _homologous series_?
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(b) The structures of some alkanes, alkenes and alcohols are shown below.


(i) Which two of these compounds, F, G, H, I, J and K, are saturated hydrocarbons? Explain your answer.
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(ii) Which one of these compounds is the main constituent of natural gas?
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(iii) Which two of these compounds are alkenes?
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(iv) Why are two compounds, I and K, not hydrocarbons?
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(c) The table gives some information about four alcohols.
[Table_1]

(i) Give the name of the alcohol with the formula $\text{C}_2\text{H}_6\text{O}$.
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(ii) A student predicts that the density of the alcohols increases as the number of carbon atoms increases.
Does the data in the table support this prediction? Explain your answer.
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(iii) Suggest a value for the boiling point of methanol.
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(d) The alcohol with the formula $\text{C}_2\text{H}_6\text{O}$ burns in a limited supply of air to form carbon monoxide and water.

(i) Complete the chemical equation for this reaction.
\[ \text{C}_2\text{H}_6\text{O} + \text{2O}_2 \rightarrow .....\text{CO} + .....\text{H}_2\text{O} \]\ [2]

(ii) State an adverse effect of carbon monoxide on health.
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Chlorine, bromine and iodine are halogens.

(a) The melting point of bromine is $-7 ^\circ \text{C}$. The boiling point of bromine is $+59 ^\circ \text{C}$.
Deduce the state of bromine at $+6 ^\circ \text{C}$. Explain your answer.
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(b) (i) Complete the word equation for the reaction of chlorine with potassium iodide.
chlorine + potassium iodide $\rightarrow$ ............................. + ............................. [2]

(ii) Suggest why iodine does not react with aqueous potassium bromide.
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(c) The structure of the dye Lithol fast yellow is shown.



Complete the table and calculate the relative molecular mass of Lithol fast yellow.
[Table_1]
\begin{array}{|c|c|c|c|}\hline \text{type of atom} & \text{number of atoms} & \text{atomic mass} & \\ \hline\text{carbon} & 13 & 12 & 13 \times 12 = 156\\ \text{hydrogen} & 10 & 1 & 10 \times 1 = 10 \\ \text{nitrogen} & 4 & 14 & 4 \times 14 = 56 \\ \text{oxygen} & & & \\ \text{chlorine} & & & \\ \hline\end{array}
relative molecular mass = ........................................ [2]

(d) Chromatography is used to separate a mixture of dyes.

(i) Draw a cross on the diagram to show where the mixture of dyes is placed at the start of the chromatography.
[1]

(ii) Suggest a suitable solvent that could be used.
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(iii) Describe what you would observe as the experiment proceeds.
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Sodium is a metal in Group I of the Periodic Table.
(a) Describe some physical and chemical properties of sodium. In your answer include
• any observations about the reactions of sodium,
• at least one word equation.
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(b) The presence of sodium in compounds can be confirmed using a flame test.
Describe how a flame test is carried out and give the result of the test for sodium.
test .................................................................................................................................................................
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result ..............................................................................................................................................................

(c) Aqueous sodium hydroxide is strongly alkaline.
(i) Which one of the following values is the pH of a strongly alkaline solution?
Put a ring around the correct answer.
pH 1 pH 2 pH 7 pH 13
(ii) Describe how you could use litmus to show that aqueous sodium hydroxide is alkaline.
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(d) Sodium sulfite, $\text{Na}_2\text{SO}_3$, reacts with hydrochloric acid.
$$\text{Na}_2\text{SO}_3(s) + 2\text{HCl}(aq) \rightarrow 2\text{NaCl}(aq) + \text{SO}_2(g) + \text{H}_2\text{O}(l)$$
Explain why this reaction could have an adverse effect on health if not carried out in a fume cupboard.
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When magnesium reacts with hydrochloric acid, the products are aqueous magnesium chloride and hydrogen.
$$\text{Mg}(s) + 2\text{HCl}(aq) \rightarrow \text{MgCl}_2(aq) + \text{H}_2(g)$$
A student used the apparatus shown to follow the progress of this reaction.


(a) Complete the diagram by putting the correct labels in the boxes.

[2]

(b) The student conducted two experiments using the same mass of magnesium in each experiment and two different concentrations of hydrochloric acid. The hydrochloric acid was in excess. All other conditions were kept constant.
The student measured the volume of hydrogen produced over a period of time. The graph shows the results.


(i) Which concentration of hydrochloric acid gave the faster initial rate of reaction?
Use the graph to explain your answer.
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(ii) Draw a curve on the graph on page 16 to show how the volume of hydrogen would change if a third experiment was carried out using 1.5 mol/dm³ hydrochloric acid and the same mass of magnesium.
[2]

(c) Give one use of hydrogen.
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[1]

(d) Explosions have occasionally been reported where tiny particles of metal dust escape into the air.
Explain why metal dust can form an explosive mixture with air.
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Solder is an alloy of lead and tin.
(a) What is the meaning of the term alloy? ............................................................................................................................................................................................ [1]
(b) State the name of another alloy. ............................................................................................................................................................................................ [1]
(c) A student heated a piece of solder carefully. The diagram shows what happens to the solder.

Use the kinetic particle theory to describe and explain what happens to the solder as it changes state.
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(d) When heated above 1744 °C, lead forms a vapour. Describe a general property of a vapour (gas) which is not shown by a solid.
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