The chlor-alkali industry
You need to know the products formed by the electrolysis of concentrated sodium chloride solution, and simple laboratory tests for them.
The electrolysis of brine
Brine is concentrated sodium chloride solution. If an electric current is passed through it, hydrogen gas forms at the negative electrode and chlorine gas forms at the positive electrode. A solution of sodium hydroxide forms. These three products have important uses in industry.
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.
The table shows the common laboratory tests for the products from the electrolysis of brine.
||Test and result
||a lighted splint pops
||damp litmus paper is bleached white
|sodium hydroxide solution
||universal indicator solution turns purple