CourseCourseConceptConceptDocumentDocument

Edexcel IGCSE Chemistry I Electrolysis Questions

Practise electrolysis questions by predicting electrode products, explaining observations and writing half-equations for ion discharge.

Syllabus
First assessment 2019
Course
Chemistry 4CH1

Exam points

  • Explain conductivity in ionic melts or solutions by referring to mobile ions.
  • Identify electrode products and observations for molten salts or aqueous solutions.
  • Write or interpret half-equations, including electron gain for reduction at the cathode.

Covered syllabus points

1.55C Covalent compounds and conductivity1.56C Ionic compounds and conductivity1.57C Anions and cations1.58C Electrolysis experiments1.59C Electrolysis half-equations1.60C Electrolysis practical

Question 1

[Maximum number: 5]

Iron metal was discovered several thousand years ago. Iron is produced industrially from iron(III) oxide by extraction using carbon.

Sodium is a metal in Group 1 of the Periodic Table. Sodium was discovered by Sir Humphrey Davy in 1807. It is produced industrially by the electrolysis of sodium chloride.

Question (a)

(a)

The diagram shows a simplified version of the Downs cell, which can be used to produce sodium industrially. The electrolyte is molten sodium chloride.

Figure for Question (a) — Edexcel IGCSE Chemistry
[ 5 ]

Question (i)

(i)

Explain why the molten electrolyte conducts electricity.

[ 2 ]

Question (ii)

(ii)

What is the formula of the cation in the electrolyte?

Figure for Question (ii) — Edexcel IGCSE Chemistry
[ 1 ]

Question (iii)

(iii)

Give ionic half-equations for the reactions at the anode and cathode.

anode……

cathode……

[ 2 ]

Question 2

[Maximum number: 8]

A scientist reacts lead(II) nitrate solution with sodium bromide solution.

This is the equation for the reaction.

Pb(NO3)2(aq)+2NaBr(aq)→PbBr2( s)+2NaNO3(aq)\mathrm{Pb}\left(\mathrm{NO}_{3}\right)_{2}(\mathrm{aq})+2 \mathrm{NaBr}(\mathrm{aq}) \rightarrow \mathrm{PbBr}_{2}(\mathrm{~s})+2 \mathrm{NaNO}_{3}(\mathrm{aq})

Question (a)

(a)

The scientist electrolyses molten lead(II) bromide using this apparatus.

Figure for Question (a) — Edexcel IGCSE Chemistry
[ 6 ]

Question (i)

(i)

Explain why lead(II) bromide needs to be molten rather than solid for electrolysis to occur.

[ 3 ]

Question (ii)

(ii)

The electrolyte is at a temperature of 400∘C400^{\circ} \mathrm{C}.

Explain a suitable material for the electrodes.

[ 2 ]

Question (iii)

(iii)

Give the half-equation that occurs at the negative electrode.

[ 1 ]

Question (b)

(b)

Bromine forms at the positive electrode.

This is the half-equation for the reaction at the positive electrode.

2Br−→Br2+2e−2 \mathrm{Br}^{-} \rightarrow \mathrm{Br}_{2}+2 \mathrm{e}^{-}
[ 2 ]

Question (i)

(i)

State what is observed at the positive electrode.

[ 1 ]

Question (ii)

(ii)

State why the half-equation represents an oxidation reaction.

[ 1 ]

Question 3

[Maximum number: 1]

This question is about Group 2 elements and their compounds.

A concentrated aqueous solution of magnesium chloride is electrolysed. Chlorine forms at the positive electrode.

Give the half-equation for the reaction at the positive electrode.

Question 4

[Maximum number: 2]

Iron metal was discovered several thousand years ago. Iron is produced industrially from iron(III) oxide by extraction using carbon.

Sodium is a metal in Group 1 of the Periodic Table. Sodium was discovered by Sir Humphrey Davy in 1807. It is produced industrially by the electrolysis of sodium chloride.

The diagram shows a simplified version of the Downs cell, which can be used to produce sodium industrially. The electrolyte is molten sodium chloride.

Figure for Question 4 — Edexcel IGCSE Chemistry

Explain why the molten electrolyte conducts electricity.

Question 5

[Maximum number: 1]

Iron metal was discovered several thousand years ago. Iron is produced industrially from iron(III) oxide by extraction using carbon.

Sodium is a metal in Group 1 of the Periodic Table. Sodium was discovered by Sir Humphrey Davy in 1807. It is produced industrially by the electrolysis of sodium chloride.

The diagram shows a simplified version of the Downs cell, which can be used to produce sodium industrially. The electrolyte is molten sodium chloride.

Figure for Question 5 — Edexcel IGCSE Chemistry

What is the formula of the cation in the electrolyte?

Figure for Question 5 — Edexcel IGCSE Chemistry

Question 6

[Maximum number: 7]

Question (a)

(a)

The teacher uses this apparatus to investigate the electrolysis of a solution of dilute hydrochloric acid.

The ammeter measures the current.

Figure for Question (a) — Edexcel IGCSE Chemistry


The teacher wants to find out if there is a relationship between current and volume of gas collected at each electrode.

She adjusts the power supply until the current is 0.1 amp.
After 5 minutes she records the volume of gas collected in syringe X and syringe Y.
The teacher repeats the experiment several times, using a different current each time.

The table gives the teacher's results for syringe Y.

Table for Question (a) — Edexcel IGCSE Chemistry
[ 6 ]

Question (i)

(i)

Plot the results for syringe Y.

[ 1 ]

Question (ii)

(ii)

Draw a circle around the anomalous result.

[ 1 ]

Question (iii)

(iii)

Draw a line of best fit.

Figure for Question (iii) — Edexcel IGCSE Chemistry
[ 1 ]

Question (iv)

(iv)

Explain a possible cause of the anomalous result, other than misreading the apparatus.

[ 2 ]

Question (v)

(v)

Deduce the relationship between current and volume of gas collected in syringe Y .

[ 1 ]

Question (b)

(b)

The ionic half-equation for the reaction that produces the gas in syringe X is

2Cl−→Cl2+2e−2 \mathrm{Cl}^{-} \rightarrow \mathrm{Cl}_{2}+2 \mathrm{e}^{-}

The ionic half-equation for the reaction that produces the gas in syringe Y is

2H++2e−→H22 \mathrm{H}^{+}+2 \mathrm{e}^{-} \rightarrow \mathrm{H}_{2}
[ 1 ]

Question (i)

(i)

Suggest why the volume of chlorine collected in syringe X is always less than the volume of hydrogen collected in syringe Y.

[ 1 ]
All question bank results loaded