 Section 1.2: Principles of chemistry 2
Electrolysis
Name __________________________________________
Date ____________
1 Electrolysis is the decomposition of some compounds using electricity.
a) Circle all the substances in the list that can be decomposed by
electrolysis.
solid ionic compounds
ionic compounds in solution
molten covalent compounds
(2 marks)
molten ionic compounds
gases
solid covalent compounds
covalent compounds in solution
b) What do these substances have in common that allows them to be
electrolysed?
(1 mark)
_________________________________________________________________
c) Label this diagram by drawing a line from each label on the right to the correct
part of the diagram.
(6 marks)
Edexcel International GCSE (9–1) Chemistry
© Hodder & Stoughton 2018
1
 Section 1.2: Principles of chemistry 2
Electrolysis
d) A student did some investigations into the electrolysis of solutions of sodium
chloride, sulfuric acid and copper sulfate. Complete the table to show the
student’s results.
(3 marks)
Solution
Ions in solution
Product(s) at cathode
sodium chloride
Na+, Cl−, H+, OH−
hydrogen gas
Product(s) at anode
sodium hydroxide solution
sulfuric acid
H+, SO42− , OH−
copper sulfate
Cu2+, SO42− , H+, OH−
oxygen gas
copper metal
e) Explain why each solution contains the ions H+ and OH−.
(1 mark)
________________________________________________________________
________________________________________________________________
2 The reactions at the cathode and anode for each investigation can be represented
by half equations. Write the half equations for:
a) the production of hydrogen gas in the electrolysis of sodium chloride
solution
(1 mark)
_________________________________________________________________
b) the production of copper metal in the electrolysis of copper sulfate
solution
(1 mark)
_______________________________________________________________________
c) the production of oxygen gas in the electrolysis of sulfuric acid solution
(1 mark)
_______________________________________________________________________
3 Explain why:
a) the reactions at the cathode are reduction reactions
(1 mark)
_______________________________________________________________________
_______________________________________________________________________
Edexcel International GCSE (9–1) Chemistry
© Hodder & Stoughton 2018
2
 Section 1.2: Principles of chemistry 2
Electrolysis
b) the reactions at the anode are oxidation reactions
(1 mark)
_______________________________________________________________________
_______________________________________________________________________
c) the anode and cathode must be made from inert substances such as carbon or
platinum.
(1 mark)
_______________________________________________________________________
_______________________________________________________________________
4 The student repeated the investigation using molten lead(II) bromide instead of a
solution of lead bromide. At the cathode lead metal was produced.
a) Write a half equation for the production of lead at the cathode during the
electrolysis.
(1 mark)
_____________________________________________________________________
b) Suggest the products that will be made if molten sodium chloride is electrolysed.
State where each product will be made.
(4 marks)
______________________________________________________________________
______________________________________________________________________
Edexcel International GCSE (9–1) Chemistry
© Hodder & Stoughton 2018
3