Electrolysis of aqueous solutions

A teacher demonstrated the electrolysis of copper chloride solution.

Figure 12 shows the apparatus.

The teacher measured the mass of the negative electrode every 60 seconds.

Chlorine gas is given off during the electrolysis of copper chloride solution.

Chlorine gas is poisonous.

Give one way of reducing the risk of harm.

Table 5 shows the results.

Plot the data from Table 5 on Figure 13.

Draw a line of best fit.

The first point has been plotted for you.

A student made the hypothesis:

‘The negative electrode will increase by a constant mass every 60 seconds.’

How do the results in Table 5 show that the hypothesis is not correct?

25 cm³ of the solution of copper chloride contained 5.5 g of copper chloride.

Calculate the concentration of the solution in g/dm³.

The teacher also electrolysed potassium chloride solution.

Hydrogen gas was given off at the negative electrode.

Why was hydrogen gas given off?

Tick () one box.

A teacher demonstrated the electrolysis of copper chloride solution.

Figure 1 shows the apparatus.

The teacher measured the mass of the negative electrode every 60 seconds.

Chlorine gas is given off during the electrolysis of copper chloride solution.

Chlorine gas is poisonous.

Give one way of reducing the risk of harm.

Table 1 shows the results.

Plot the data from Table 1 on Figure 2.

Draw a line of best fit.

The first point has been plotted for you.

A student made the hypothesis:

‘The negative electrode will increase by a constant mass every 60 seconds.’

How do the results in Table 1 show that the hypothesis is not correct?

25 cm³ of the solution of copper chloride contained 5.5 g of copper chloride.

Calculate the concentration of the solution in g/dm³.

The teacher also electrolysed potassium chloride solution.

Hydrogen gas was given off at the negative electrode.

Why was hydrogen gas given off?

Tick () one box.

Copper bromide solution is electrolysed using inert electrodes. Figure 11 shows the apparatus.

Which particles carry the electrical charge through the metal wire? Tick (✓) one box.

There are four ions in copper bromide solution:

• Cu²⁺

• Br^–

• H⁺

• OH^–

Two of these ions are formed when a water molecule breaks down. The symbol equation when a water molecule breaks down is:

Complete the word equation for the breakdown of a water molecule.

Copper ions and bromide ions carry the electrical charge through the solution. The formula of a copper ion is Cu²⁺ The formula of a bromide ion is Br^– What is the formula of copper bromide? Tick (✓) one box.

Explain why copper ions (Cu²⁺) move to the negative electrode.

Complete the sentence. Choose the answer from the box.

At the negative electrode copper metal is produced when the

What happens to the mass of the negative electrode during electrolysis? Tick (✓) one box.

There are four ions in copper bromide solution:

• Cu²⁺

• Br^–

• H⁺

• OH^–

What is produced at the positive electrode when copper bromide solution

Tick (✓) one box.

During electrolysis ions are discharged at the electrodes to produce elements. A student investigates the electrolysis of sodium chloride.

Sodium chloride solution conducts electricity. Complete the sentence.

Figure 5 shows the apparatus for the electrolysis of sodium chloride solution.

Suggest an element that could be used to make the inert electrodes.

Complete the half equation for the production of chlorine (Cl₂) at the positive electrode.

Sodium chloride solution has a pH of 7 During the electrolysis of sodium chloride solution:

• hydrogen gas is produced at the negative electrode

• the pH of the solution increases.

Explain why.

This question is about electrolysis. Figure 14 shows the apparatus used to investigate the electrolysis of potassium sulfate solution.

Potassium sulfate contains K⁺ and SO₄^2– ions. What is the formula of potassium sulfate? Tick (✓) one box.

What are the volumes of gases collected in the electrolysis experiment? Use Figure 14.

A student made the following hypothesis: ‘The volumes of gases collected in this electrolysis experiment are in the same ratio as hydrogen atoms to oxygen atoms in a water molecule.’ Explain how the volumes of gases collected in the experiment in Figure 14 support the student’s hypothesis. Use your answer to Question 06.2

The experiment is repeated 4 times. The volumes of oxygen collected in the 4 experiments are:

The mean volume of oxygen collected in the 4 experiments is 9 cm³ The measure of uncertainty is the range of a set of measurements about the mean.

What is the measure of uncertainty in the 4 experiments?

Tick (✓) one box.

Calculate the mass of potassium sulfate needed to make 1.0 dm³ of solution.

This question is about electrolysis. Figure 2 shows the apparatus used to investigate the electrolysis of potassium sulfate solution.

Potassium sulfate contains K⁺ and SO₄^2– ions. What is the formula of potassium sulfate? Tick (✓) one box.

What are the volumes of gases collected in the electrolysis experiment? Use Figure 2.

A student made the following hypothesis: ‘The volumes of gases collected in this electrolysis experiment are in the same ratio as hydrogen atoms to oxygen atoms in a water molecule.’ Explain how the volumes of gases collected in the experiment in Figure 2 support the student’s hypothesis. Use your answer to Question 02.2

The experiment is repeated 4 times. The volumes of oxygen collected in the 4 experiments are:

The mean volume of oxygen collected in the 4 experiments is 9 cm³ The measure of uncertainty is the range of a set of measurements about the mean.

What is the measure of uncertainty in the 4 experiments? Tick (✓) one box.

Calculate the mass of potassium sulfate needed to make 1.0 dm³ of solution.

This question is about electrolysis.

Complete the sentence. Choose the answer from the box.

Copper chloride can conduct electricity when in solution or

Figure 1 shows the apparatus used for the electrolysis of copper chloride solution.

There are four ions in copper chloride solution:

• Cu²⁺

• Cl^–

• H⁺

• OH^–

Why do Cl^– ions and OH^– ions move to the positive electrode?

Where do the H⁺ and OH^– ions come from in the electrolysis of copper chloride solution? Tick (✓) one box.

Which ion produces a metal? Tick (✓) one box.

Figure 2 shows the apparatus during the electrolysis of copper chloride solution.

Describe what is seen at each electrode during the electrolysis of copper chloride solution. Positive electrode

Negative electrode

500 cm³ of copper chloride solution contains 6.50 g of copper chloride. Calculate the mass of copper chloride in 40.0 cm³ of this copper chloride solution.

This question is about the electrolysis of aqueous solutions.

Hydrogen gas and chlorine gas are produced when sodium chloride solution is electrolysed.

Hydrogen ions (H⁺) are attracted to the negative electrode. The half equation for the reaction at the negative electrode is:

What type of reaction happens at the negative electrode? Give the reason for your answer.

Chloride ions are attracted to the positive electrode. Complete the half equation for the production of chlorine gas (Cl₂).

Hydrogen gas and oxygen gas are produced when sodium sulfate solution is electrolysed. Explain how oxygen gas is produced in the electrolysis of sodium sulfate solution.

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.

This question is about electrolysis. A student investigates the mass of copper produced during electrolysis of copper chloride solution. Figure 12 shows the apparatus.

Which gas is produced at the positive electrode (anode)? Tick one box.

Copper is produced at the negative electrode (cathode). What does this tell you about the reactivity of copper? Tick one box.

Table 4 shows the student’s results.

Determine the mean mass of copper produced after 3 minutes.

Calculate the mass X of copper produced in Experiment 2 after 5 minutes. Use Table 4 on page 19

The copper chloride solution used in the investigation contained 300 grams per dm³ of solid CuCl₂ dissolved in 1 dm³ of water. The students used 50 cm³ of copper chloride solution in each experiment. Calculate the mass of solid copper chloride used in each experiment.

This question is about electrolysis. A student investigates the mass of copper produced during electrolysis of copper chloride solution. Figure 1 shows the apparatus.

Which gas is produced at the positive electrode (anode)? Tick one box.

02

Copper is produced at the negative electrode (cathode). What does this tell you about the reactivity of copper? Tick one box.

Table 1 shows the student’s results.

Determine the mean mass of copper produced after 3 minutes.

Calculate the mass X of copper produced in Experiment 2 after 5 minutes. Use Table 1 on page 3

The copper chloride solution used in the investigation contained 300 grams per dm³ of solid CuCl₂ dissolved in 1 dm³ of water. The student used 50 cm³ of copper chloride solution in each experiment. Calculate the mass of solid copper chloride used in each experiment.