Chemistry - Complete d-block Question with Solution | TestHub

Since, ${\mathrm{OH}}^{-}$are generated from weak acid $\left({\mathrm{H}}_2\mathrm{O}\right)$, a weak acid $($ like ${\mathrm{CO}}_2)$ should be used to remove it because of strong acid $(\mathrm{HCl})$ reverse the reaction. $\mathrm{KOH}$ increases the concentration of ${\mathrm{OH}}^{-}$, thus again shifts the reaction in backward side. ${\mathrm{CO}}_2$ combines with ${\mathrm{OH}}^{-}$to give carbonate which is easily removed. ${\mathrm{SO}}_2$ reacts with water to give strong acid, so it cannot be used.