Question

Choose and give the correct answer from the following : platinum, ${\mathrm{PbBr}}_2$, ${\mathrm{Cl}}_2$, ${\mathrm{O}}_2$, cathode, anode.

The gas liberated when molten sodium chloride is electrolysed.

Answer 1

• Electrolysis is a process in which electricity is passed through a substance to effect a chemical change.
• When sodium chloride is electrolysed, it decomposes to form sodium metal and chlorine gas.
• Electrolysis of sodium chloride :
  $2\mathrm{NaCl}(\mathrm{aq}.)\stackrel{\mathrm{Electrolysis}}{\to }2\mathrm{Na}\left(\mathrm{s}\right)+{\mathrm{Cl}}_2\left(\mathrm{g}\right)$
• At cathode :
  $2{\mathrm{Na}}^{+}(\mathrm{aq}.)+2{\mathrm{e}}^{-}\to \mathrm{Na}\left(\mathrm{s}\right)$
• At anode :
  $2{\mathrm{Cl}}^{-}(\mathrm{aq}.)+2{\mathrm{e}}^{-}\to {\mathrm{Cl}}_2\left(\mathrm{g}\right)$
• Hence, the chlorine gas is liberated at anode when molten sodium chloride is electrolysed.