SODIUM HYDROXIDE is formed near the cathode. why?

Electrolysis of concentrated sodium chloride solutions (brine) produces chlorine gas, hydrogen gas and aqueous sodium hydroxide.

2NaCl(aq) + 2H2O(l) -----> H2(g) + Cl2(g) + 2NaOH(aq)

Cl2(g) is produced at the anode (positive electrode).

H2(g) and NaOH(aq) are produced at the cathode (negative electrode).

 

At cathode:

Sodium ions and hydrogen ions (from the water) are attracted to the negative cathode. It is much easier for a hydrogen ion to pick up an electron than for a sodium ion. So this reaction is:

2H+  + 2e -------------> H2(g)

As the hydrogen ions are converted into hydrogen gas, the water equilibrium tips to the right to replace them.

Equilibrium shifts to produce more hydroxide ions as H+ ions are removed during hydrolysis. The net effect of this is that there is formation of sodium ions and hydroxide ions around the cathode, i.e formation of sodium hydroxide solution around the cathode.

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