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Chemistry · Ch 4 — Hydrogen

Preparation of Hydrogen

4.2

Preparation of Hydrogen

The purest hydrogen -- greater than 99.9% -- is obtained by electrolysis: either water containing a trace of acid or alkali to make it conducting, or an aqueous solution of sodium hydroxide or potassium hydroxide, is electrolysed using a nickel anode and an iron cathode. The half-reactions are:

At anode: 2 OH−→H2O+12O2+2e−\text{At anode: } 2\,OH^- \rightarrow H_2O + \tfrac{1}{2}O_2 + 2e^-

At cathode: 2 H2O+2e−→2 OH−+H2\text{At cathode: } 2\,H_2O + 2e^- \rightarrow 2\,OH^- + H_2

Overall: H2O→H2+12O2\text{Overall: } H_2O \rightarrow H_2 + \tfrac{1}{2}O_2 …

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