Using electrolysis to extract metals

This question is about metals.

Complete the sentence.

Choose the answer from the box.

Iron is extracted from iron oxide by reduction with carbon.

Why is iron extracted by reduction with carbon?

Tick () one box.

Aluminium is extracted by the electrolysis of aluminium oxide.

Figure 8 shows the apparatus used to extract aluminium.

The mixture of aluminium oxide and cryolite has a lower melting point than aluminium oxide alone.

Why is the melting point lowered?

Tick () one box.

After some time, the positive electrodes need to be replaced.

Why must the positive electrodes be replaced?

Tick () one box.

Aluminium can be mixed with other metals to form alloys.

How does the hardness of an alloy of aluminium compare with the hardness of pure aluminium?

Tick () one box.

Aluminium can form an alloy with silver.

Figure 9 shows how the melting point of the alloy changes with the percentage (%) of silver in the mixture.

Describe how the melting point of the alloy changes as the percentage of silver in the mixture increases.

Use data from Figure 9.

This question is about metals.

Iron is extracted from iron oxide by reduction with carbon.

Why can iron be extracted by reduction with carbon?

Answer in terms of reactivity.

Aluminium is extracted by the electrolysis of aluminium oxide.

Figure 4 shows the apparatus used to extract aluminium.

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

Oxygen gas is produced at the positive electrode.

Write a balanced half equation for the production of oxygen at the positive electrode.

Chromium is extracted by reacting chromium oxide with aluminium.

The equation for the reaction is:

Which substance in the equation is reduced?

Table 3 shows the relative cost of extracting equal masses of aluminium, chromium and iron.

Give one reason for the difference in the cost of extracting aluminium and iron.

Use Table 3.

Give one reason for the difference in the cost of extracting aluminium and chromium

Use Table 3.

Metals are mixed together to form alloys.

Explain why alloys are harder than pure metals.

In the Earth most metals are found as compounds.

Name one metal that is found in the Earth as the metal itself.

Figure 9 shows a reactivity series.

Suggest the most economical method for extracting metal Z from an oxide of metal Z

Figure 10 shows the electrolysis cell used to extract aluminium from aluminium oxide.

Name substance X shown in Figure 10.

Explain what happens to the positive carbon electrodes during the extraction of aluminium from aluminium oxide.

The formula of aluminium oxide is Al₂O₃

Write a half equation for the reaction at the negative electrode in Figure 10.

This question is about extraction of metals.

Aluminium is extracted from a molten mixture of aluminium oxide and cryolite using electrolysis. Figure 12 shows the electrolysis cell.

Complete the sentence.

The extraction of aluminium is expensive because the process uses

Oxygen is produced at the positive carbon electrodes. The oxygen reacts with the carbon electrodes. Which gas is produced when oxygen reacts with the positive carbon electrodes?

Titanium is extracted from titanium chloride by reacting titanium chloride with sodium.

The reaction between titanium chloride and sodium is carried out in an

Suggest why the reaction is carried out in an inert atmosphere.

Complete the sentence. Choose the answer from the box.

Balance the equation for the reaction.

Copper is extracted from copper oxide by reacting copper oxide with carbon.

Figure 13 shows the apparatus.

The equation for the reaction is:

In an experiment 15.9 g of copper oxide and 1.2 g of carbon reacted. 12.7 g of copper was produced in the reaction.

Calculate the mass of carbon dioxide produced in this experiment.

Explain why the mass of the contents in the crucible changed during the experiment.

What happens to copper oxide in the reaction? Give one reason for your answer. Use the equation for the reaction. Tick (✓) one box.

This question is about the extraction of aluminium.

An aluminium atom is represented as: 27 A l 13 Give the number of electrons and neutrons in the aluminium atom.

Aluminium is extracted by the electrolysis of a molten mixture of aluminium oxide and cryolite. Figure 11 shows the cell used for the electrolysis.

Aluminium is produced by the reduction of aluminium oxide (Al₂O₃). What is meant by the term reduction?

Oxygen is formed at the positive carbon electrodes. Explain why the positive carbon electrodes must be continually replaced.

A substance conducts electricity because of free moving, charged particles. What are the free moving, charged particles in a:

• carbon electrode (made from graphite)

• molten mixture of aluminium oxide and cryolite

• metal wire?

Molten mixture of aluminium oxide and cryolite

This question is about the extraction of aluminium.

An aluminium atom is represented as: 27 A l 13 Give the number of electrons and neutrons in the aluminium atom.

Aluminium is extracted by the electrolysis of a molten mixture of aluminium oxide and cryolite. Figure 1 shows the cell used for the electrolysis.

Aluminium is produced by the reduction of aluminium oxide (Al₂O₃). What is meant by the term reduction?

Oxygen is formed at the positive carbon electrodes. Explain why the positive carbon electrodes must be continually replaced.

A substance conducts electricity because of free moving, charged particles. What are the free moving, charged particles in a:

• carbon electrode (made from graphite)

• molten mixture of aluminium oxide and cryolite

• metal wire?

Molten mixture of aluminium oxide and cryolite

This question is about salts and electrolysis. A student wants to make copper chloride crystals. The student adds excess copper oxide to some hot acid. The student stirs the mixture.

Which acid should the student use? Tick (✓) one box.

Suggest how the student would know that excess copper oxide has been added.

There are four more stages, A, B, C and D, to make copper chloride crystals. The stages A, B, C and D are not in the correct order. Stage A Partially evaporate by heating with a water bath Stage B Filter the mixture into an evaporating basin Stage C Leave to crystallise Stage D Remove and dry the crystals

Put stages A, B, C and D in the correct order.

Molten copper chloride can be electrolysed. State the product at each electrode when molten copper chloride is electrolysed.

Negative electrode Positive electrode

A solution of copper chloride is electrolysed. Figure 3 shows a graph of the increase in mass of the negative electrode. This increase is shown over a time of 10 minutes.

Calculate the gradient of the line in Figure 3. Use the equation:

Aluminium is produced by electrolysis of a molten mixture. Complete the sentence. Choose the answers from the box.

This question is about electrolysis.

Some metals are extracted from molten compounds using electrolysis. Why is electrolysis used to extract some metals?

Aluminium is produced by electrolysis of a molten mixture. What two substances does the molten mixture contain?

Copper and chlorine are produced when molten copper chloride is electrolysed. Complete the half equation for the reaction at each electrode.

Half equation at negative electrode

Half equation at positive electrode

Figure 4 shows the apparatus a student used to electrolyse copper chloride solution.

The student:

• measured the mass of copper deposited on the negative electrode after 60 minutes

• compared the mass deposited with the expected value.

Suggest two reasons why the mass deposited was different from the expected value.

Figure 5 shows the expected mass of copper produced each minute.

Determine the expected mass of copper after 24 hours. Use Figure 5.

Silver nitrate solution is electrolysed. Figure 6 shows the change in mass of the negative electrode over 10 hours.

Determine the mass of the negative electrode at the start of the experiment. Use Figure 6.

Calculate the gradient of the line in Figure 6. Give the unit.