If an electric current is passed through concentrated sodium chloride solution, hydrogen gas forms at the negative electrode and chlorine gas forms at the positive electrode. A solution of sodium hydroxide forms.
You might have expected sodium metal to be deposited at the negative electrode. But sodium is too reactive for this to happen, so hydrogen is given off instead.
During electrolysis:
- Hydrogen ions H+ (from the water) are discharged at the negative electrode as hydrogen gas, H2
- Chloride ions Cl– are discharged at the positive electrode as chlorine gas, Cl2
- Sodium ions Na+ and hydroxide ions OH– (from the water) stay behind - they form sodium hydroxide solution, NaOH
The three products of electrolysis
The three products of the electrolysis of concentrated sodium chloride solution have important uses in the chemical industry:
- Hydrogen is used as a fuel and for making ammonia
- Chlorine is used to kill bacteria in water, and to make bleach and plastics
- Sodium hydroxide is used to make soap and bleach
Now try a Test Bite.
Read on if you're taking the higher paper.
Posted on 07:54 / 1
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