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OCR GCSE Combined Science

Topic questions Chemical changes Electrolysis of aqueous solutions

Electrolysis of aqueous solutions

5 questions · 38 marks · about 45 minutes

Electrolysis of aqueous solutions questions

TopicElectrolysis of aqueous solutions

OCR J250 Electrolysis of aqueous solutions 5 questions

Chemistry Paper 9 June 2025 Higher tier, Question 15 13 marks

Sodium hydroxide, NaOH, and calcium hydroxide, Ca(OH)2, are ionic compounds that dissolve in water to form alkaline solutions.

(a)

Why are solutions of sodium hydroxide and calcium hydroxide called alkalis?

[1]
Reveal mark scheme Mark scheme for question 15(a)
(b)

Explain why the formula of sodium hydroxide is NaOH but the formula of calcium hydroxide is Ca(OH)2.

[3]
Reveal mark scheme Mark scheme for question 15(b)
(c)

The electrolysis of a sodium hydroxide solution produces hydrogen at the cathode rather than sodium.

Explain why.

[3]
Reveal mark scheme Mark scheme for question 15(c)
(d)

When carbon dioxide is bubbled through a calcium hydroxide solution it turns cloudy white.

This is the equation for the reaction.

Question 15, shown as an image
(d)(i)

Which chemical in the equation turns the solution cloudy white?

[1]
Reveal mark scheme Mark scheme for question 15(d)(i)
(d)(ii)

What is the alternative name for the calcium hydroxide solution?

[1]
Reveal mark scheme Mark scheme for question 15(d)(ii)
(d)(iii)

The calcium hydroxide solution contains 0.038 g of calcium hydroxide.

Calculate the maximum mass of carbon dioxide that can react with the calcium hydroxide solution.

Give your answer to 2 significant figures.

Relative atomic mass (Ar): H = 1.0 C = 12.0 O = 16.0 Ca = 40.1

[4]
Reveal mark scheme Mark scheme for question 15(d)(iii)

Chemistry Paper 9 June 2024 Higher tier, Question 12 8 marks

Figure for question 12
(a)

Describe what happens when solid potassium bromide is heated up until it melts into a liquid.

Use ideas about the particle model.

[3]
Reveal mark scheme Mark scheme for question 12(a)
(b)

Explain why potassium bromide must be molten for electrolysis to happen.

[1]
Reveal mark scheme Mark scheme for question 12(b)
(c)

State the product made at the cathode and write the half equation for the reaction.

[2]
Reveal mark scheme Mark scheme for question 12(c)
(d)

The electrolysis is repeated with a solution of potassium bromide.

A student thinks that the same product will be formed at the cathode.

Explain why the student is incorrect.

Name of the different product formed........

[2]
Reveal mark scheme Mark scheme for question 12(d)

Chemistry Paper 10 November 2021 Higher tier, Question 3 1 mark

An aqueous solution of sodium chloride, NaC l, is electrolysed using inert electrodes.

Which product is formed at the cathode?

A Chlorine

B Hydrogen

C Oxygen

D Sodium

Question 3, shown as an image
[1]
Reveal mark scheme Mark scheme for question 3

Chemistry Paper 9 November 2020 Higher tier, Question 17 10 marks

Figure for question 17
(a)

Explain the term electrolysis.

[2]
Reveal mark scheme Mark scheme for question 17(a)
(b)

Electrolysis involves the reactions of cations and anions.

Describe the difference between cations and anions.

[1]
Reveal mark scheme Mark scheme for question 17(b)
(c)

The electrolysis of molten potassium chloride makes potassium at the cathode.

(c)(i)

Write the balanced half equation for the formation of potassium.

[1]
Reveal mark scheme Mark scheme for question 17(c)(i)
(c)(ii)

State and explain if this equation shows oxidation or reduction.

[2]
Reveal mark scheme Mark scheme for question 17(c)(ii)
(d)
Figure for question 17
[2]
Reveal mark scheme Mark scheme for question 17(d)
(e)

Name the product formed at the anode when an aqueous solution of potassium chloride, KC l (aq), is electrolysed.

Give a reason for your answer.

[2]
Reveal mark scheme Mark scheme for question 17(e)

Chemistry Paper 9 June 2019 Higher tier, Question 14 6 marks

Brine is the name given to the solution formed when sodium chloride, NaC l, dissolves in water.

(a)

During the electrolysis of sodium chloride solution, two ions are attracted to the negative electrode (cathode).

(a)(i)

Identify the two ions attracted to the negative electrode (cathode).

[2]
Reveal mark scheme Mark scheme for question 14(a)(i)
(a)(ii)

State and explain which product is formed at the negative electrode (cathode).

[2]
Reveal mark scheme Mark scheme for question 14(a)(ii)
(b)
Figure for question 14
[2]
Reveal mark scheme Mark scheme for question 14(b)

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