Cambridge IGCSE Chemistry - 0620 - Core Paper 3 2016 Summer Zone 1

The structures of some substances containing chlorine are shown.

(a) Answer the following questions about these substances.
(i) Which substance is a diatomic molecule?
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(ii) Which substance represents part of an ionic structure?
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(iii) Which substance is an element?
Explain your answer.
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(iv) Determine the simplest formula for substance D.
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(b) The symbols for two isotopes of chlorine are shown.
$$\frac{35}{17} \text{Cl} \quad \frac{37}{17} \text{Cl}$$
(i) How do these two isotopes differ in their atomic structure?
............................................................................................................................. [1]
(ii) Determine the number of neutrons present in one atom of the isotope $$\frac{35}{17} \text{Cl}$$.
............................................................................................................................. [1]
(iii) Draw the electronic structure of a chlorine atom. Show all shells and all electrons.
............................................................................................................................. [2]

A bicycle maker wants to choose a suitable material to make bicycle frames. The table shows the properties of some materials that could be used.

[Table_1]

(a) Which material is the most suitable for making the bicycle frame?

Explain your answer using information from the table.
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(b) Aluminium is extracted from aluminium oxide by electrolysis.

(i) State the name of the main ore of aluminium.
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(ii) Suggest why aluminium is extracted by electrolysis and not by reduction with carbon.
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(iii) Molten aluminium oxide is electrolysed using graphite electrodes.

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

(c) The diagram shows the changes of state when zinc vapour is cooled slowly to room temperature.



Explain what happens during these changes in terms of

The table shows some properties of the Group I metals.

[Table_1]

(a) (i) Describe the trend in boiling points of the Group I metals.
............................................................................................................................... [1]

(ii) Predict the density of caesium.
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(iii) Deduce the state of caesium at 20ºC.
Explain your answer.
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(b) Complete the word equation for the reaction of rubidium with water.
rubidium + water → ........................................ + ........................................ [2]

(c) The dye, indigo tin, is formed when compound F is exposed to air. The structure of compound F is shown below.



Complete the table and calculate the relative molecular mass of compound F.

[Table_2]

relative molecular mass = ........................................ [2]

(d) Three dye mixtures, J, K and L, were spotted onto a piece of chromatography paper. Three pure dyes, X, Y and Z, were also spotted onto the same piece of paper.
The diagram shows the results of this chromatography.



(i) Suggest why the base line was drawn in pencil and not in ink.
............................................................................................................................... [1]

(ii) Which dye mixture, J, K or L, contains a dye which did not move during this chromatography?
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(iii) Which dye mixture, J, K or L, contains both dye X and dye Y?
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(iv) Which dye mixture, J, K or L, does not contain dye Z?
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(a) (i) Which two of these compounds are alcohols? Explain your answer.
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[2]
(ii) Which two of these compounds are saturated hydrocarbons?
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[1]
(b) Methanol and ethanol are alcohols in the same homologous series.
Complete the following sentence about a homologous series using words from the list.
alcohols chemical compounds elements functional mixtures physical
A homologous series is a family of similar ............................................ with similar .......................................... properties due to the same .......................................... group.
[3]

(c) Ethene is an alkene.
(i) Draw the structure of ethene showing all atoms and all bonds.
[1]
(ii) Describe how aqueous bromine is used to show that ethene is an unsaturated compound.
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............................................................................................................................
[2]
(iii) Ethene is manufactured by cracking.
State the conditions needed for cracking.
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[1]
(iv) Complete the chemical equation for the cracking of hexadecane, $C_{16}H_{34}$, to form propene and one other hydrocarbon.
$C_{16}H_{34} ightarrow C_{3}H_{6} + ext{.....................}$
[1]

The Group VII elements are called the halogens.

(a) Describe the trends in
• the physical properties of the halogens,
• the reactivity of halogens with other halide ions.
Include a relevant word equation in your answer.
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(b) Iodine reacts with hot concentrated nitric acid.

\[ \text{I}_2 + 10\text{HNO}_3 \rightarrow 2\text{HIO}_3 + 4\text{H}_2\text{O} + 10\text{NO}_2 \]
(i) Explain why this reaction could have an adverse effect on health if not carried out in a fume cupboard.
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............................................................................................................................... [2]
(ii) Nitric acid is strongly acidic.
Which one of the following pH values represents a strongly acidic solution?
Put a ring around the correct answer.
pH 1 pH 7 pH 9 pH 13 [1]
(iii) Nitric acid reacts with zinc oxide.
State the names of the products of this reaction.
................................................ and ................................................ [2]

Ammonia is manufactured by the reaction of nitrogen with hydrogen in the presence of a catalyst.

(a) What is the purpose of a catalyst?
.................................................................................................................................................. [1]

(b) The reaction is reversible.
Complete the equation below by adding the sign for a reversible reaction.
\[ \text{N}_2 + 3\text{H}_2 \rightarrow 2\text{NH}_3 \] [1]

(c) The energy level diagram for this reaction is shown.
Is this reaction exothermic or endothermic?
Give a reason for your answer.



.................................................................................................................................................. [1]
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(d) The graph shows how the percentage yield of ammonia changes with temperature when the pressure is kept constant.



(i) Describe how the percentage yield of ammonia changes with temperature.
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(ii) Determine the percentage yield of ammonia at 350\degree C.
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(e) Describe a test for ammonia.
test..........................................................................................................................
result....................................................................................................................... [2]

(f) Ammonia is a weak base.
Describe how you would measure the pH of an aqueous solution of a weak base using Universal Indicator.
.................................................................................................................................................. [2]

(g) Complete the chemical equation for the reaction of ammonia with chlorine.
........\text{NH}_3 + 3\text{Cl}_2 \rightarrow \text{N}_2 + ......\text{HCl} [2]

Calcium carbonate reacts with dilute hydrochloric acid.

$$\text{CaCO}_3(\text{s}) + 2\text{HCl}(\text{aq}) \rightarrow \text{CaCl}_2(\text{aq}) + \text{CO}_2(\text{g}) + \text{H}_2\text{O}(\text{l})$$
A student investigated this reaction by measuring the volume of carbon dioxide released every minute at constant temperature.

(a) Draw a diagram of the apparatus that the student could use to investigate this reaction. [2]

(b) The graph shows the results of this reaction using three samples of calcium carbonate of the same mass: large pieces, medium-sized pieces, and small pieces.



(i) Which sample, large, medium or small pieces, gave the fastest initial rate of reaction? Use the graph to explain your answer. [2]

(ii) The experiment was repeated using powdered calcium carbonate of the same mass. Draw a line on the grid above to show how the volume of carbon dioxide changes with time for this experiment. [2]

(iii) At what time was the reaction just complete when small pieces of calcium carbonate were used? [1]

(c) When calcium carbonate is heated strongly, calcium oxide is formed.

(i) Give one use of calcium oxide. [1]

(ii) What type of oxide is calcium oxide? Explain your answer. [2]

A teacher passed hydrogen gas over hot copper(II) oxide.

$\text{CuO(s)} + \text{H}_2\text{(g)} \rightarrow \text{Cu(s)} + \text{H}_2\text{O(g)}$

(a) Which substance is reduced in this reaction?
Explain your answer.
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........................................................................................................................... [2]

(b) The diagram shows the apparatus used.



The hydrogen was passed over the hot copper(II) oxide until the reaction was complete.

(i) As the experiment proceeds, suggest what happens to the mass of copper(II) oxide.
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(ii) Suggest why electrical heating is used in this experiment and not a Bunsen burner.
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(iii) Describe the chemical test for the presence of water.
test..........................................................................................................................
result........................................................................................................................ [2]