Question

Which one results in the cathode product while electrolysis of a dilute solution of sodium chloride?

• A. chlorine gas
  
• B. hydrogen gas
  
• C. sodium gas
  
• D. oxygen gas
  

Answer 1

The correct option is B hydrogen gas

Hydrogen gas results in the cathode product while electrolysis of a dilute solution of sodium chloride.
At cathode, two reduction reactions compete with each other. One is reduction of Na(I) ions to Na
$N{a}^{+}+e^{-}\to Na{E}_{red}^o=-2.71V$
The other reaction is the reduction of water to hydrogen gas.
$2_{2}O+2e^{-}\to H2+2O{H}^{-}{E}_{red}^o=-0.83V$
The standard reduction potential for the reduction of water is higher than that for reduction of $N{a}^{+}$
Water has much greater tendency to get reduced than $N{a}^{+}$ ions. hence, the reduction of water to liberate hydrogen is the reaction at cathode for the electrolysis of aq $NaCl$.