During electrolysis of sodium chloride ______ gas liberates at the anode

Extraction of metals at the top of the activity series by electrolysis of their fused compounds.  For example to extract Na from NaCl, fused NaCl is electrolysed with steel cathode  ( − )  and graphite rod ( + ) . The metal (Na) will be deposited at cathode and chlorine liberated at anode.

$\mathrm{At} \mathrm{Cathode}; 2{\mathrm{Na}}^{+}+2{\mathrm{e}}^{-}\to 2\mathrm{Na}$

At Anode;  $2{\mathrm{Cl}}^{-}\to {\mathrm{Cl}}_2+2{\mathrm{e}}^{-}$