CBSE 2023 · Region 5 · Set 1 · Q4 · 1 mark

Four half reactions I to IV are shown below : I. $\displaystyle 2 \mathrm{Cl} l^{-} \rightarrow \mathrm{Cl}_{2}+2 \mathrm{e}^{-}$ II. $\displaystyle 4 \mathrm{OH}^{-} \rightarrow \mathrm{O}_{2}+2 \mathrm{H}_{2} \mathrm{O}+2 \mathrm{e}^{-}$ III. $\displaystyle \mathrm{Na}^{+}+\mathrm{e}^{-} \rightarrow \mathrm{Na}$ IV. $\displaystyle 2 \mathrm{H}^{+}+2 \mathrm{e}^{-} \rightarrow \mathrm{H}_{2}$ Which two of these reactions are most likely to occur when concentrated brine is electrolysed?

CBSE Class 12 Chemistry past-paper question from the 2023board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.