Concentration of 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.

Lithium hydroxide reacts with sulfuric acid to produce lithium sulfate. The equation for the reaction is:

What type of reaction is this?

Relative atomic masses (A_r): H = 1 O = 16 S = 32

Relative atomic mass (A_r): O = 16

Give your answer to 2 significant figures.

A solution of lithium sulfate contains 0.30 g of lithium sulfate in 25 cm³. Calculate the concentration of lithium sulfate in g/dm³.

Lithium hydroxide reacts with sulfuric acid to produce lithium sulfate. The equation for the reaction is:

What type of reaction is this?

Relative atomic masses (A_r): H = 1 O = 16 S = 32

Relative atomic mass (A_r): O = 16

Give your answer to 2 significant figures.

A solution of lithium sulfate contains 0.30 g of lithium sulfate in 25 cm³. Calculate the concentration of lithium sulfate in g/dm³.

Acids react with some metals to produce soluble salts. A student adds magnesium to hydrochloric acid until no more acid reacts and

The equation for the reaction is:

The reaction between magnesium and hydrochloric acid is a redox reaction. Explain what happens to the magnesium atoms in this reaction.

0.72 g of magnesium is added to 100 cm³ of hydrochloric acid. The hydrochloric acid is in excess. Calculate the concentration of the magnesium chloride (MgCl₂) solution produced

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.

A student investigated the temperature change when metal X was added to copper sulfate solution. This is the method used.

1. Add 25 cm³ of copper sulfate solution to a beaker.

2. Measure the temperature of the copper sulfate solution.

3. Add 1.0 g of metal X and stir.

4. Measure the highest temperature reached when metal X is added to copper sulfate solution.

5. Repeat steps 1 to 4 with different metals.

Figure 1 shows the apparatus used.

Figure 2 shows the thermometer reading of the copper sulfate solution at the start of the investigation.

The highest temperature reached when metal X was added to copper sulfate solution was 35.5 °C Determine the temperature change when metal X is added to copper sulfate solution. Use Figure 2. Highest temperature = 35.5 °C

Give two variables the student should keep the same in this investigation.

The student repeated the experiment with metal Y. Table 1 shows four results for metal Y.

Calculate the mean temperature change for metal Y. Do not include the anomalous result in your calculation.

The more reactive the metal added to copper sulfate solution, the greater the temperature change. Figure 3 shows a reactivity series.

Figure 3

Calcium Magnesium Zinc Copper Silver least reactive

The student repeated the experiment. The student added:

• magnesium to copper sulfate solution

• an unknown metal A to copper sulfate solution.

Table 2 shows the results.

The student concludes metal A is zinc. Give one reason why the student is correct. Use Figure 3 and Table 2.

The student did the experiment with silver and copper sulfate solution. What happens to the temperature of the mixture? Use Figure 3. Tick (✓) one box.

Suggest one reason why the student should not add potassium metal to copper sulfate solution.

100 cm³ of the copper sulfate solution contains 1.8 g of copper sulfate. Calculate the mass of copper sulfate in 25 cm³ of this copper sulfate solution.

This question is about reactions of metals. Figure 7 shows what happens when calcium, copper, magnesium and zinc are added to hydrochloric acid.

What is the order of decreasing reactivity of these four metals? Tick (✓) one box.

A student wants to make a fair comparison of the reactivity of the metals with hydrochloric acid.

Name two variables that must be kept constant.

What is the independent variable in this reaction?

Predict the reactivity of beryllium compared with magnesium. Give a reason for your answer. Use the periodic table.

A solution of hydrochloric acid contains 3.2 g of hydrogen chloride in 50 cm³ Calculate the concentration of hydrogen chloride in g per dm³

This question is about reactions of metals. Figure 1 shows what happens when calcium, copper, magnesium and zinc are added to hydrochloric acid.

What is the order of decreasing reactivity of these four metals? Tick (✓) one box.

A student wants to make a fair comparison of the reactivity of the metals with hydrochloric acid.

Name two variables that must be kept constant.

What is the independent variable in this reaction?

Predict the reactivity of beryllium compared with magnesium. Give a reason for your answer. Use the periodic table.

A solution of hydrochloric acid contains 3.2 g of hydrogen chloride in 50 cm³ Calculate the concentration of hydrogen chloride in g per dm³

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.