The equivalent weight of chlorine molecule in the equation
3Cl₂ +6NaOH → 5NaCl + NaClO₃ +3H₂O

$3\stackrel{0}{{\mathrm{Cl}}_2}+6\mathrm{NaOH} \to 5\mathrm{Na}\stackrel{-1}{\mathrm{Cl}} + \mathrm{Na}\stackrel{+5}{\mathrm{Cl}}{\mathrm{O}}_3 +3{\mathrm{H}}_2\mathrm{O}$

Oxidation: $6{\mathrm{OH}}^{-}+1/2{\mathrm{Cl}}_2⟶2{\mathrm{ClO}}_3^{-}+5{\mathrm{e}}^{-}+3{\mathrm{H}}_2\mathrm{O}$

Reduction: $\frac{5}{2}{\mathrm{Cl}}_2+5{\mathrm{e}}^{-}⟶5{\mathrm{Cl}}^{-}$

3 moles of Cl₂​ & 5 moles of electrons are involved in the redox reaction.

Molar mass of Cl₂​=71

∴ Equivalent mass of Cl_2​=$\frac{3\times 71}{5}=42.6\mathrm{g}/\mathrm{mol}$