Electrolysis of aqueous solutions

Lithium reacts with chlorine to produce lithium chloride.

Figure 10 shows models of chlorine and of lithium chloride.

Draw one line from each substance to the type of bonding in the substance.

Lithium chloride can also be produced by reacting lithium carbonate with an acid.

Which acid reacts with lithium carbonate to produce lithium chloride?

Tick () one box.

Hydrochloric acid

Nitric acid

Sulfuric acid

What type of substance is lithium chloride?

Tick () one box.

Acid

Alkali

Salt

Figure 11 shows the electrolysis of lithium chloride solution.

Lithium chloride solution contains Li⁺ ions and Cl⁻ ions.

Chloride ions move to the positive electrode to produce chlorine.

Explain why chloride ions move to the positive electrode.

Hydrogen gas and chlorine gas are produced during the electrolysis of lithium chloride solution.

Draw one line from each gas to the result of the test for that gas.

Why is hydrogen gas produced at the negative electrode?

Tick () one box.

Hydrogen is less reactive than lithium.

Hydrogen has the same reactivity as lithium.

Hydrogen is more reactive than lithium.

Hydrogen reacts with chlorine to produce hydrogen chloride. A hydrogen atom has 1 electron in the outer shell.

A chlorine atom has 7 electrons in the outer shell.

Complete the dot and cross diagram for a hydrogen chloride molecule.

Use the symbols O and X to represent electrons.

An aqueous solution of sodium chloride can be electrolysed.

Figure 12 shows the apparatus.

The electrodes in Figure 12 are made of graphite.

Graphite is a good conductor of electricity.

Give one other reason why graphite electrodes are used.

Do not refer to conduction of electricity in your answer.

The electrolysis of an aqueous solution of sodium chloride produces chlorine, hydrogen and one other substance.

What is the other substance produced in the electrolysis of an aqueous solution of sodium chloride?

Tick () one box.

Hydrochloric acid

Sodium

Sodium hydroxide

Water

Write the half equation for the production of chlorine gas at the positive electrode.

Hydrogen gas is produced at the negative electrode in the electrolysis of an aqueous solution of sodium chloride.

Explain why.

A student electrolysed copper sulfate solution using inert electrodes.

Figure 8 shows the apparatus used.

Copper was produced at the negative electrode.

Oxygen was produced at the positive electrode.

Copper sulfate solution contains copper ions and hydrogen ions.

Why is copper produced instead of hydrogen during the electrolysis of copper sulfate solution?

Tick (✓) one box.

Copper is less reactive than hydrogen.

Copper has the same reactivity as hydrogen.

Copper is more reactive than hydrogen.

The student measured how the mass of copper produced varied with time.

Table 1 shows the results.

What conclusion can be made about how the mass of copper produced varied with time?

Use Table 1.

Predict the time taken to produce 0.20 g of copper.

Use Table 1.

0.5 dm³ of a solution of copper sulfate contains 3.2 g of copper sulfate.

Calculate the concentration of the solution of copper sulfate.

Use the equation:

Choose the unit from the box.

Copper sulfate has the formula CuSO₄

Calculate the percentage (%) by mass of copper in CuSO₄

Give your answer to 3 significant figures.

Relative atomic mass (A_r): Cu = 63.5

Relative formula mass (M_r): CuSO₄ = 159.5

This question is about electrolysis.

Figure 9 shows the electrolysis of molten potassium chloride using inert electrodes.

Why must potassium chloride be molten during the electrolysis?

Why are inert electrodes used in electrolysis?

A gas is released during the electrolysis of molten potassium chloride.

Describe the test to identify the gas released.

Give the result if the gas is present.

Potassium is produced at the negative electrode.

Write the half equation for the reaction at the negative electrode during the electrolysis of molten potassium chloride.

What type of reaction occurs at the negative electrode?

An aqueous solution of potassium chloride was electrolysed.

Hydrogen gas was produced at the negative electrode.

Explain why hydrogen gas is produced during the electrolysis of an aqueous solution of potassium chloride.

50 cm³ of potassium chloride solution contains 0.030 moles of potassium chloride.

Calculate the concentration of the potassium chloride solution in g/dm³.

Relative formula mass (M_r) of potassium chloride = 74.5

Concentration = g/dm³ _________________

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.

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.

A student investigated the electrolysis of potassium chloride solution.

Figure 1 shows the apparatus used.

The student used the piece of equipment labelled A to measure the volume of gas collected.

What is the piece of equipment labelled A ?

Tick (✓) one box.

What does the circuit symbol B represent?

Complete the sentence.

Choose the answer from the box.

Direct current (dc) is supplied to the circuit.

What is direct current?

Tick (✓) one box.

Potassium chloride solution contains potassium (K⁺) ions and chloride (Cl^–) ions.

Why are chloride ions attracted to the positive electrode?

Hydrogen gas is produced at the negative electrode.

Which test should the student use to identify hydrogen gas?

Tick (✓) one box.

Hydrogen ions and potassium ions move to the negative electrode.

Hydrogen gas is produced at the negative electrode.

Why is hydrogen gas produced at the negative electrode?

Tick (✓) one box.

The student measured the volume of gas collected at each electrode every minute for 25 minutes.

Figure 2 shows the results.

Describe one similarity and one difference in the volume of hydrogen and the volume of chlorine collected during the 25 minutes.

Use Figure 2.

A student investigated the electrolysis of potassium chloride solution.

Figure 10 shows the apparatus used.

Why are inert electrodes used?

The student measured the volume of gas collected at each electrode for 25 minutes.

Figure 11 shows the results.

Compare the rate of collection of hydrogen and of chlorine.

Give one similarity and one difference in the rate of collection of the gases.

The rate of production of hydrogen and of chlorine at the electrodes is the same.

Explain how the graph on Figure 11 shows that chlorine is more soluble than hydrogen.

Explain why hydrogen gas is produced at the negative electrode in the electrolysis of potassium chloride solution.

Write the half equation for the production of chlorine gas at the positive electrode.