Using electrolysis to extract metals

Metals are found in the Earth’s crust as the metal itself or as a metal compound.

Why is gold found in the Earth as the metal itself?

Aluminium is extracted from aluminium oxide by electrolysis.

The electrolyte is a molten mixture of aluminium oxide and cryolite.

Aluminium cannot be extracted from aluminium oxide using carbon.

Give one reason why.

Give two reasons why large amounts of energy are needed for the electrolysis of aluminium oxide.

Recycling aluminium needs less energy than extracting new aluminium.

Table 4 shows the energy needed for 1 kg of aluminium to be:

extracted

recycled.

Calculate the percentage decrease in energy needed when aluminium is recycled instead of extracted.

Give your answer to 2 significant figures.

Metals are found in the Earth’s crust as the metal itself or as a metal compound.

Why is gold found in the Earth as the metal itself?

Aluminium is extracted from aluminium oxide by electrolysis.

The electrolyte is a molten mixture of aluminium oxide and cryolite.

Aluminium cannot be extracted from aluminium oxide using carbon.

Give one reason why.

Give two reasons why large amounts of energy are needed for the electrolysis of aluminium oxide.

Recycling aluminium needs less energy than extracting new aluminium.

Table 1 shows the energy needed for 1 kg of aluminium to be:

extracted

recycled.

Calculate the percentage decrease in energy needed when aluminium is recycled instead of extracted.

Give your answer to 2 significant figures.

This question is about metal extraction and recycling.

Most metals are found in the Earth as metal compounds.

Why is gold found in the Earth as the metal itself?

How is aluminium extracted from aluminium compounds?

Tick (✓) one box.

By displacement

By electrolysis

By reduction with carbon

Iron is extracted from iron oxide.

An oxide ion is an oxygen atom that has gained two electrons.

What is the formula of an oxide ion?

Tick (✓) one box.

O₂ O²⁻ O²⁺

Iron oxide is heated with carbon to produce iron and carbon dioxide.

The word equation for the reaction is:

Which substance is oxidised in the reaction?

Iron is used to make steel.

Scrap steel can be recycled.

Give two environmental advantages of recycling scrap steel instead of making new steel from iron.

Table 3 shows information about scrap steel in one year.

Calculate the percentage (%) of scrap steel that was recycled in one year.

Figure 5 shows metal food and drink cans.

The metal cans are made from steel or aluminium.

Which property of steel means that steel can be separated from aluminium at a recycling centre?

This question is about metal extraction.

Copper compounds can be extracted from low-grade copper ores using: plants bacteria.

Name the process that uses plants to extract copper compounds from low-grade copper ores.

Name the process that uses bacteria to extract copper compounds from low-grade copper ores.

Why are processes using plants and bacteria now used to extract copper compounds from low-grade copper ores?

Give one advantage of extracting copper compounds using plants and bacteria rather than using traditional methods.

Aluminium is extracted by the electrolysis of a molten mixture of aluminium oxide and cryolite.

Explain why the electrolyte used is a mixture of aluminium oxide and cryolite.

Do not refer to cost in your answer.

Oxygen is produced at the positive electrodes.

Explain why the positive electrodes must be continually replaced.

This question is about chemical processes.

Iron can be extracted from iron oxide using carbon.

The word equation for the reaction is:

iron oxide + carbon → iron + carbon dioxide

Why can iron be extracted from iron oxide using carbon?

Tick (✓) one box.

Iron is less reactive than carbon.

Iron has the same reactivity as carbon.

Iron is more reactive than carbon.

Which reactant is reduced?

Tick (✓) one box.

Carbon

Carbon dioxide

Iron

Iron oxide

Aluminium is manufactured by the electrolysis of a molten mixture of aluminium oxide and cryolite.

Figure 4 shows the apparatus.

What are the positive electrodes in Figure 4 made of?

Tick (✓) one box.

Aluminium

Carbon

Copper

Iron

Large amounts of energy are used in the extraction of aluminium from aluminium oxide.

Give two reasons why.

Electrolysis is only possible when an ionic compound is molten or in aqueous solution.

Explain why.

You should refer to ions and charge in your answer.

An aqueous solution of copper chloride is electrolysed using inert electrodes.

What is meant by ‘inert’?

Table 2 shows information about the products of the electrolysis of an aqueous solution of copper chloride.

Complete Table 2.

This question is about the extraction of metals.

Name the process that uses bacteria to extract metals.

Iron can be extracted from iron oxide using carbon.

The word equation for the reaction is:

iron oxide + carbon → iron + carbon dioxide

Explain why this reaction is both oxidation and reduction.

Give one reason why some metals cannot be extracted from their oxides using carbon.

Aluminium is manufactured by the electrolysis of a molten mixture of aluminium oxide and cryolite.

Explain why cryolite is used.

Aluminium is produced at the negative electrode.

Complete the half equation for the reaction.

You should balance the equation.

Al³⁺ + ____________ → ____________

This question is about substances found in the Earth’s crust.

Aluminium silicate is a compound found in the Earth’s crust.

The formula of aluminium silicate is Al₂SiO₅

What is the total number of atoms in the formula Al₂SiO₅?

Tick (✓) one box.

3 5 7 8

Table 2 shows the percentage of some elements found in the Earth’s crust.

Calculate the simplest whole number ratio for the percentage of silicon to the percentage of aluminium in the Earth’s crust.

Simplest whole number ratio for: percentage of silicon: percentage of aluminium = _____________: _____________

Iron is found as iron oxide in the Earth’s crust.

Iron can be extracted by heating iron oxide with carbon.

Why is iron oxide reacted with carbon to extract iron?

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Iron is less reactive than carbon.

Iron has the same reactivity as carbon.

Iron is more reactive than carbon.

The word equation for the reaction to extract iron is:

iron oxide + carbon iron + carbon dioxide

Which reactant is reduced?

Tick (✓) one box.

Carbon

Carbon dioxide

Iron

Iron oxide

The symbol equation for the reaction to extract iron is:

What is the value of X ?

Tick (✓) one box.

2 3 4 5

Aluminium is found as aluminium oxide in the Earth’s crust.

Figure 8 shows the apparatus used for the process to extract aluminium from aluminium oxide.

Name the process used to extract aluminium from aluminium oxide.

What are the positive electrodes made of in this process?

Tick (✓) one box.

Aluminium

Carbon

Copper

Cryolite

Large amounts of energy are used in the process in Figure 8.

Give two ways energy is used in the process.

Diamond and silicon dioxide are also found in the Earth’s crust.

Figure 9 represents the structure of diamond and the structure of silicon dioxide.

Compare the structure and bonding of diamond with the structure and bonding of silicon dioxide.

This question is about the extraction of metals.

Traditional mining methods extract copper from high-grade copper ores.

Phytomining is a method used to extract copper from low-grade copper ores.

Explain one advantage of using phytomining compared with using traditional mining methods to extract copper.

Do not refer to cost in your answer.

Describe how copper compounds are obtained by phytomining.

Electrolysis is one method of obtaining copper from solutions of copper compounds.

Figure 6 shows the apparatus used.

Graphite is a good conductor of electricity.

Give one other reason why graphite is used for the electrodes.

A gas is produced at the positive electrode. The gas is tested with damp litmus paper. The gas bleaches the damp litmus paper.

Identify the copper compound in solution.

Give one reason for your answer.

Scrap iron is used in a reaction to obtain copper from solutions of copper compounds.

Name this type of reaction.

Aluminium is extracted by the electrolysis of a molten mixture of aluminium oxide and cryolite.

Explain why a mixture rather than pure aluminium oxide is electrolysed.

The positive electrodes are made of carbon.

Explain why the positive electrodes wear away during the process.