GCSEScienceWJECScience (Double Award)ChemistryExam QuestionsChemical Bonding, Application Of Chemical Reactions & Organic ChemistryMetals & Their Extraction

Metals & Their Extraction (WJEC GCSE Science (Double Award): Chemistry): Exam Questions

Exam code: 3430

3 hours24 questions

2 marks

Draw a line to link each of the following metallic properties to its meaning.

One has been done for you.

Figure: Matching diagram with two columns — the left column lists three property terms (malleable, ductile, thermal conductor) and the right column lists six meanings in scrambled order (can be hammered into shape, can be melted, can be pulled into wires, can transfer electricity, can be burned, can transfer heat), with a line already drawn from "malleable" to "can be hammered into shape" as the given worked example, and lines still to be drawn from "ductile" and "thermal conductor" to their correct meanings

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4 marks

Alternative methods of extracting copper

As the Earth's supply of high-grade copper ores continues to decline, alternative methods such as phytomining and bioleaching are becoming more commonly used to extract copper from low-grade ores.

Phytomining

Photograph of a green flowering plant growing in reddish-brown soil containing low-grade copper ore, illustrating the plants used to absorb and concentrate copper in phytomining.

Phytomining involves growing plants in soils that contain low-grade copper ores. The plants absorb the copper ions through their roots and they are concentrated inside the plants' cells.

The plants are then harvested and burned. The ash that is left behind contains higher concentrations of copper ions than the low-grade ores in the soil.

The copper ions are washed out from the ash using sulfuric acid, forming a concentrated solution of copper(II) sulfate.

Scrap iron is then added to the copper(II) sulfate solution to allow the copper to be collected.

The main drawback to phytomining as an alternative method of copper extraction is that the process is dependent on the successful growth of the plants used for the extraction.

Bioleaching

Photograph of a mountainous mining site with snow-covered ground, open industrial tanks or settling ponds, processing structures and pipes, and a large rocky spoil heap beneath a clear blue sky.

Bioleaching is a very simple process that uses bacteria to extract copper from the minerals found within the lowest grade copper ores.

The bacteria are added to tanks of water containing the ores. There they feed on the nutrients found within the minerals in these ores, causing the copper ions to separate out.

An acidic solution is formed during the process. This contains a higher concentration of copper ions than the low-grade ores.

The solution formed is called a leachate, which is why the process is called bioleaching.

Copper is collected from the leachate solution by mixing it with iron.

The main drawback to bioleaching as an alternative method of copper extraction is that the process is extremely slow and therefore not efficient.

(i) Tick (✓) the box next to the correct statement.

phytomining uses lower grade ores than bioleaching	$□$
bioleaching conserves supplies of the lowest grade metal ores	$□$
phytomining conserves supplies of high-grade metal ores	$□$
bioleaching uses high-grade metal ores	$□$
phytomining uses the lowest grade metal ores	$□$

[1]

(ii) State whether you agree with the following statement. Give a reason for your answer.

'Phytomining and bioleaching both involve biological processes'

Agree Yes / No

Reason ..................................................................................................................

[1]

(iii) Suggest a reason why phytomining might not be a suitable method for extracting metals in some countries, even if they have supplies of the low-grade metal ores.

.........................................................................................

[1]

(iv) Although effective in extracting copper, suggest a reason why bioleaching is an extremely slow process.

.........................................................................................

[1]

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2 marks

Explain why iron can be used in the last stage of both the phytomining and bioleaching methods of copper extraction.

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2 marks

The Red Metals

Copper, brass and bronze are known as the 'red metals'. This is because they stand out against other metals due to their characteristic reddish colour.

From construction and architecture to telecommunications and machinery, there is no denying the importance of these 'red metals' in our daily lives.

However, whilst they might all look similar, copper, brass and bronze have very different compositions and properties.

Copper

Most of the world's copper is extracted from copper ores. Once extracted, copper has many uses in its pure form.
In addition to its various applications, copper is present in the other red metals – brass and bronze.
Copper is best known for its electrical and thermal conductivity, malleability and ductility, and resistance to corrosion.
Today it is most commonly found in electrical materials, roofing, plumbing and industrial machinery.

Brass

Brass is made by adding varying amounts of zinc to copper.
Depending on the zinc content, different types of brass can be created and used for different applications.
The more zinc that is added to the brass, the stronger, more ductile, more malleable and lighter in colour it becomes.
Brass is commonly used in architecture for its decorative features as well as in manufacturing, construction and in the electrical and plumbing industries.

Bronze

Bronze is made by mixing copper with tin and other metals such as aluminium, zinc and manganese.
The properties of bronze vary, depending on its specific composition.
Bronze is commonly known for its hardness, as well as being highly ductile, brittle and corrosion resistant.
Bronze is used in architecture as well as for making sculptures, electrical contacts, machine tools and coins.

Tick (✓) to show whether the properties of copper, brass and bronze are fixed or can vary.

	Properties are fixed	Properties can vary
copper	$□$	$□$
brass	$□$	$□$
bronze	$□$	$□$

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1 mark

Tick (✓) the correct statement.

copper, bronze and brass are all metal alloys	$□$
copper and bronze are both metal alloys	$□$
copper and brass are both metal alloys	$□$
bronze and brass are both metal alloys	$□$

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1 mark

Give the letter of the structure, A, B or C, that best represents brass.

Structure .....................................................

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11a

5 marks

Corey and Bailey used the following apparatus to obtain copper from copper(II) chloride solution.

Figure: Electrolysis apparatus diagram — a beaker of copper(II) chloride solution (containing dissolved Cu2+ and Cl- ions shown scattered through the liquid) with two electrodes dipping in from above, connected to a power supply. The left electrode is labelled "positive electrode (+)" and the right electrode is labelled "negative electrode (−)"

(i)

electrolysis copper anode
cathode chlorine displacement
copper(II) chloride neutralisation

Choose words from the box to complete the following sentences.

The electrolyte used in this process is ............................................................

Copper is formed at the negative electrode. This electrode is called the ........................................

The breaking down of a compound using an electric current is called .........................................

[3]

(ii) Copper(II) chloride contains the ions Cu²⁺ and Cl^-.

Give the formula of copper(II) chloride.

.................................................................

[1]

(iii) During the process, copper ions become copper atoms by gaining electrons.

Tick (✓) the box next to the equation that shows this.

Cu − 2e^- → Cu²⁺	$□$
Cu + 2e^- → Cu²⁺	$□$
Cu²⁺ + 2e^- → Cu	$□$
Cu²⁺ − 2e^- → Cu	$□$

[1]

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11b

4 marks

The diagram represents the industrial extraction of aluminium from its ore.

Figure: Diagram of an electrolysis cell for aluminium extraction, showing molten aluminium oxide inside the cell with bubbles of oxygen rising near the electrodes, and a layer of molten aluminium collecting at the bottom of the cell

(i) Give the reason why the aluminium oxide must be molten during the extraction.

Tick (✓) the correct box.

to release the oxygen gas from the aluminium oxide	$□$
to allow the aluminium ions and oxide ions to move	$□$
to allow the aluminium to leave the cell	$□$
to speed up the process	$□$

[1]

(ii) Put a number in the box to balance the equation that represents the overall reaction taking place.

2Al₂O₃ → [ ] Al + 3O₂

[1]

(iii) Tick (✓) the boxes next to the two factors that are important when choosing the location for aluminium plants in the UK.

Aluminium plants in the UK should be close to

landfill sites	$□$
power stations	$□$
limestone quarries	$□$
oil refineries	$□$
coastal ports	$□$
coal mines	$□$

[2]

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11c

2 marks

Aluminium is commonly used to make overhead power cables.

Figure: Photograph of electricity pylons carrying overhead power cables against a blue sky

Other than being a good electrical conductor, give two properties which make aluminium a suitable material for making overhead power cables.

Property 1 ................................................................................................................................

Property 2 .................................................................................................................................

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12a

6 marks

When a mixture of iron(III) oxide and aluminium powder is heated, the following reaction takes place.

iron(III) oxide + aluminium → iron + aluminium oxide

The reaction is commonly called the thermite reaction. The photographs show the reaction taking place and how it is used in the repair of railway lines.

Two photographs. The first shows the thermite reaction in progress — a crucible producing intense white sparks and molten metal. The second shows the thermite process being used on a railway track, with a mould clamped around a rail joint and the reaction taking place above it to weld the rail

(i) Explain why iron is formed during the reaction.

....................................................................................................

[2]

(ii) Complete and balance the equation for the reaction.

Fe₂O₃ + 2Al → ...................................................................

[2]

(iii) Calculate the percentage by mass of iron in iron(III) oxide, Fe₂O₃.

A_r(Fe) = 56 A_r(O) = 16

Percentage = ........................................................ %

[2]

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12b

5 marks

Clare and Frankie were investigating the reactivity of metals. They carried out a series of displacement reactions in a dropping tile. In each test they placed a small piece of metal into a solution of the nitrate of a different metal as shown.

A 4×4 dropping tile diagram. The four columns are labelled with metals placed in each: copper, tin, iron, zinc (left to right). The four rows are labelled with the nitrate solution in each: zinc nitrate solution, iron(II) nitrate solution, tin nitrate solution, copper(II) nitrate solution (top to bottom) — giving 16 wells in total, one for every metal/solution combination

(i) It was not necessary to carry out all of the tests. Place crosses ( $\times$ ) on the diagram to show which tests did not need to be carried out.

Explain your choice.

.............................................................................................................

[2]

(ii) The equation shows the reaction between iron and copper(II) nitrate solution.

2Fe + 3Cu(NO₃)₂ → 2Fe(NO₃)₃ + 3Cu

Use the equation to calculate the maximum mass of copper that you would expect to be formed when 0.224 g of iron is added to excess copper(II) nitrate solution.

A_r(Fe) = 56 A_r(Cu) = 63.5

Maximum mass of copper = ........................................................ g

[3]

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12c

4 marks

The photograph shows how the electrolysis of zinc chloride can be carried out in the laboratory.

Photograph of a small electrolysis set-up — two carbon electrodes clamped and dipped into a white dish containing zinc chloride, connected by wires to a power supply with a small bulb in the circuit to show current is flowing

(i) Balance the equation that represents the reaction taking place at the anode.

Use the equation to explain the meaning of the term oxidation.

......Cl^- → Cl₂ + ......e^-

......................................................................................

[2]

(ii) The following method can be used to calculate the mass of zinc produced during the process.

Record the mass of the cathode before placing it into the electrolyte
Allow the process to run to completion
Remove the cathode from the electrolyte and record its new mass
Calculate the increase in mass

I. It is often found that the increase in mass measured using this method is greater than expected. Suggest a reason for this.

.........................................................................................................

[1]

II. Suggest why this method cannot be used to measure the mass of chlorine produced during the process.

............................................................................................................

[1]

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17a

4 marks

Nathan and Simon were investigating the reactivity of metals.

In one experiment, they investigated the effect of adding dilute hydrochloric acid to four different metals, A, B, C and D.

The diagram shows the observations made.

Figure: Four test tubes labelled A, B, C, D, each containing dilute hydrochloric acid. Tube A shows a moderate number of gas bubbles rising. Tube B shows a large number of gas bubbles rising (most vigorous reaction). Tube C shows no bubbles at all (no reaction). Tube D shows a small number of gas bubbles rising

(i) They used the same volume of acid in each tube. Give two other ways they controlled the dilute hydrochloric acid to ensure a fair test.

[2]

(ii) Use the observations to list the metals in order of their reactivity. Give the reason for your choice.

Most reactive ...................................

...................................

Least reactive ...................................

Reason ........................................................................................

[2]

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17b

5 marks

In a second experiment, Nathan and Simon used the following apparatus to investigate the temperature rise when metals A, B, C and D were added to hydrochloric acid.

Figure: Diagram of a polystyrene cup inside a beaker, with a thermometer inserted through gaps at the top (no lid fitted over the cup, and the thermometer bulb positioned above the liquid rather than immersed in it), labelled thermometer, lid (shown separately, not fitted), polystyrene cup, beaker

(i) Identify the error in the way the apparatus is set up and state how this would affect the results collected.

Error .............................................................................................

Effect ................................................................................................

[2]

(ii) Once they had set up their apparatus correctly, they obtained the following results.

Metal	Temperature rise (°C)
Metal	Test 1	Test 2	Test 3	Mean
A	22	21	......................	22
B	40	38	36	38
C	0	0	0	0
D	15	9	13	14

I. Identify the anomalous result from metals B, C and D.

Metal .................................................... Test .....................................................

[1]

II. Calculate the missing result for metal A.

Temperature rise for test 3 = ....................................................... °C

[1]

III. Zinc is more reactive than metals C and D but less reactive than metals A and B. Use this information to predict the temperature rise that would be expected for zinc.

Temperature rise for zinc ....................................................... °C

[1]

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18a

1 mark

The Transition Metals

Schematic periodic table divided into three labelled blocks: the s-block on the left, the d-block across the centre, and the p-block on the right; the s- and p-blocks are shaded.

The elements in the Periodic Table can be divided into three blocks: the s-block, the d-block and the p-block.

The s-block and d-block contain only metallic elements. The p-block contains both metallic and non-metallic elements.

The transition metals are found within the d-block and are the metallic elements that serve as a bridge or 'transition' between the two sides of the table. They include the elements iron, silver, gold, vanadium and titanium.

The transition metals have similar properties to each other. These include high melting point, high density, good conductivity and malleability. The transition metals also have unique properties, making them different from the main group metals, including the ability to form compounds with different colours and different oxidation states.

Table 1 gives the properties of some transition metals and some Group 1 metals.

Table 1

Element	Melting point (°C)	Boiling point (°C)	Oxidation states	Colours of compounds formed
iron	1536	2861	+2, +3	green and brown
lithium	180	1342	+1	white
potassium	63	760	+1	white
sodium	98	883	+1	white
titanium	1660	3287	+3, +4	violet and white
vanadium	1910	3407	+3, +4, +5	green, blue and yellow

Tick (✓) the statement that best describes where metals are positioned within the Periodic Table.

the s-block, p-block and d-block	$□$
the s-block and p-block only	$□$
the s-block only	$□$
the d-block and p-block only	$□$
the p-block only	$□$

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18b

1 mark

Name the element in Table 1 that is a liquid over the biggest temperature range.

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18c

2 marks

Tick (✓) the two statements that correctly describe the oxidation states of the metals listed in Table 1.

the Group 1 metals and transition metals all have a +1 oxidation state	$□$
the transition metals all have a +3 oxidation state	$□$
the Group 1 metals all have a +1 oxidation state	$□$
iron and lithium have the same oxidation states	$□$
the Group 1 metals and transition metals all have a +4 oxidation state	$□$

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18d

2 marks

Consider the following statement.

'It is possible to tell the Group 1 and transition metals apart by the colour of the compounds they form.'

Use the information in Table 1 to give one reason to agree and one reason to disagree with this statement.

Reason to agree ...............................................................................

Reason to disagree .............................................................................................................

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20a

1 mark

An alloy is a material composed of a mixture of elements, at least one of which is a metal. The table lists the composition and common uses of different alloys containing silver and gold.

Name of alloy	Composition of alloy by mass (%)	Uses of alloy
amalgam	mercury 48 %, silver 25 %, tin 15 %, copper 12 %	dental fillings, mining
green gold	gold 75 %, silver 6-24 %, copper ................ %	Nobel Prize medals, decoration
nordic gold	gold 89 %, aluminium 5 %, zinc 5 %, tin 1 %	coins, decoration
solder	tin 90 %, silver 5 %, copper 5 %	joining electrical components
sterling silver	silver 92.5 %, platinum 4 %, germanium 1.5-3 %, zinc 0.5-2 %	decoration, plumbing, instruments, jewellery
white gold	gold 75 %, palladium 10 %, nickel 10 %, zinc 5 %	decoration, jewellery

Circle the number of alloys that contain an element from Group 4 of the Periodic Table.

0 1 2 3 4 5 6

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20b

1 mark

Circle the correct percentage range for the mass of copper that can be found in green gold.

0-25% 1-19% 19-25% 6-24%

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20c

1 mark

Tick ( $✓$ ) the statement that best describes the composition of the alloys listed.

Statement	Tick
the alloys all contain at least one metal	$□$
the alloys all contain at least two metals	$□$
the alloys all contain at least three metals	$□$
the alloys all contain at least four metals	$□$

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20d

1 mark

Tick ( $✓$ ) the statement that best describes the decorative uses of the alloys listed.

Statement	Tick
all of the alloys are used for decorative purposes	$□$
all of the alloys containing gold are used for decorative purposes	$□$
all of the alloys containing silver are used for decorative purposes	$□$
none of the alloys containing silver are used for decorative purposes	$□$

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20e

2 marks

A solder joint in an electrical circuit contains 0.00011 kg of silver.

Use this information and the composition of solder given in the table to calculate the mass of tin in the solder joint.

Mass = .......................................... kg

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Student	Answer
Yena	4.4 g
Charlie	4.5 g
Tomasz	5.0 g

Time (s)	Mass of copper formed (mg)
Time (s)	1	2	Mean
0	0	0	0
10	2.8	3.2	3.0
20	4.8	5.0	4.9
30	8.2	7.8	8.0
40	10.8	11.2	11.0
50	12.9	13.1	13.0
60	15.8	16.0	15.9

Name of metal ore	Metal extracted from ore	Formula of ore
anglesite	lead	PbCl₂
copper pyrite	copper	CuFeS₂
cryolite	aluminium	Na₃AlF₆
salt petre	potassium	KNO₃
syberite	gold	AgAuTe₂
tin pyrite	tin	Cu₂FeSnS₄

Metal	Potential difference (V)	Direction of electron flow
A	0.3	copper → metal A
B	0.6	metal B → copper
C	1.1	metal C → copper
D	0.8	copper → metal D

Pair of metals in the cell	Potential difference (V)	Direction of electron flow
W and X	1.2	W → X
W and Y	0.9	Y → W
W and Z	0.8
Y and Z		Y → Z

Metal	Melting point	Electrical conductivity	Thermal conductivity	Density	Resistance to corrosion
aluminium	high	good	good	low	good
copper	high	good	good	high	good
titanium	high	good	good	low	good

	magnesium	iron	copper
magnesium nitrate		$\times$	$\times$
iron(II) nitrate	$✓$		$\times$
copper(II) nitrate	$✓$	$✓$

2Cl^- + 2e^- → 2Cl	$□$
Cl^- + e^- → Cl^2-	$□$
2Cl^- → Cl₂ + 2e^-	$□$
Cl^- + e^- → Cl	$□$
Cl^- → Cl₂ + 2e^-	$□$

Metal	Temperature before the reaction (°C)	Temperature after the reaction (°C)	Temperature increase (°C)
zinc	20	...................................	14
magnesium	19	39	20
iron	19	24	5