Question

1.

a) Complete the following table summarizing the general properties of the electrodes in an electrolytic cell.

Electrode		Oxidation or Reduction	Sign of Electrode
Anode
Cathode

b) Sodium metal is produced commercially by the electrolysis of molten sodium chloride. The by-product of the reaction is chlorine gas. (a) Write the oxidation and reduction half-reactions for the electrolysis of molten sodium chloride. (b) Identify the substance that is oxidized and the substance that is reduced. (c) Write the balanced chemical equation for the overall reaction.

c) Sodium metal is easily oxidized—it is a very reactive metal. Sodium reacts spontaneously with water at room temperature to give sodium hydroxide and hydrogen gas. Would you expect to observe sodium metal in the electrolysis of aqueous sodium chloride? Explain.

Answer 1

Cathode electrode have negative charge and all reduction reaction occurs here.

Anode have positive charge and all oxidation reactions occurs here.

Now,

a)

Half reaction at cathode :

2Na+(l) + 2ele- ====> 2Na(s)

Half reaction at Anode :

2Cl- (l) =====> Cl2 (g) + 2ele-

b)

Since, Na+ accept electron and therefore changes to Na. So, Na+ undergo reduction.

And Cl- loses electron and changes to Cl2 gas, therefore Cl- undergo oxidation.

c)

The balanced chemical equation for overall reaction would be,

2Cl-(l) + 2Na+(l) ======> Cl2(g) + 2Na(s)

d) from the  fact that sodium is very reactive and easily oxidized we concluded that it is very difficult to reduce sodium cations.

Therefore, in aqueous solution of NaCl, reduction of water to hydrogen gas is more favorable than reduction of sodium cations to sodium metal.

So, we would not expect to observe sodium metal in the electrolysis of aqueous sodium chloride.