Core Knowledge – Topic 3 Electrolysis

90) What is an electrolyte?

Answer 90
An ionic compound in either the molten state or dissolved in water.

91) What is electrolysis?

Answer 91
A chemical process that decomposes an electrolyte using electrical energy from a direct current (DC) supply.

92) What are positively charged ions called?

Answer 92
Cations.

93) What are negatively charged ions called?

Answer 93
Anions.

94) What is the positive electrode called?

Answer 94
Anode.

95) What is the negative electrode called?

Answer 95
Cathode.

96) How do the ions move during electrolysis?

Answer 96

The cations migrate to the cathode.

The anions migrate to the anode.

97) What products are formed in the electrolysis of the following electrolytes:

  1. Copper chloride solution
  2. Sodium chloride solution
  3. Sodium sulphate solution
  4. Water acidified with sulphuric acid
  5. Molten lead bromide
Answer 97

 AnodeCathodeLeft in solution
1ChlorineCopper 
2ChlorineHydrogenSodium hydroxide
3OxygenHydrogen 
4OxygenHydrogen 
5BromineLead 

98) What is the cathode half equation when water is electrolysed?

Answer 98
2H+ + 2e– → H2

99) What is the anode half equation when water is electrolysed?

Answer 99
2O2- → O2 + 4e–

100) Define oxidation and reduction.

Answer 100
Oxidation is loss of electrons and reduction is gain of electrons.

101) When water is electrolysed are the hydrogen ions oxidised or reduced?

Answer 101
Reduced.

102) Does oxidation happen at the anode or cathode?

Answer 102
Anode.

103) When purifying copper using electrolysis  would you make the impure copper the anode or the cathode?

Answer 103
Anode.

104) Write the half equation for the formation of copper at the cathode.

Answer 104
Cu2+ + 2e– → Cu