Chlor-Alkali Process

A series of free IGCSE Chemistry Activities and Experiments (Cambridge IGCSE Chemistry).

Electrolysis of Brine
Brine is concentrated sodium chloride solution. If an electric current is passed through it, hydrogen gas forms at the negative electrode (cathode) and chlorine gas forms at the positive electrode (anode). A solution of sodium hydroxide forms.
These three products - hydrogen, chlorine and sodium hydroxide - have important uses in the chemical industry:
Hydrogen: making ammonia, margarine
Chlorine: killing bacteria in drinking water and swimming pools, making bleach, disinfectants, hydrochloric acid, plastics
Sodium hydroxide: making soap, paper, ceramics

Questions

1. Write down the half equations for the cathode and anode.

Answers

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  1. At the cathode: 2Cl^- (aq) → Cl₂ (g) + 2e^-
     At the anode: 2H⁺ (aq) + 2e^- → H₂ (g)

The chlor-alkali industry
Flowing mercury plant and membrane plant

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