MHTCET 11 Apr 2026 Shift 1 Paper

Concept:Sodium carbonate is a salt of a strong base and a weak acid, so its aqueous solution is basic due to hydrolysis.Explanation:When $\mathrm{Na}_{2}\mathrm{CO}_{3}$ dissolves in water, it dissociates completely:$$< br> \mathrm{Na}_{2}\mathrm{CO}_{3} \rightarrow 2\mathrm{Na}^{+} + \mathrm{CO}_{3}^{2-} < br>$$The carbonate ion undergoes hydrolysis with water:$$< br> \mathrm{CO}_{3}^{2-} + \mathrm{H}_{2}\mathrm{O} \rightleftharpoons \mathrm{HCO}_{3}^{-} + \mathrm{OH}^{-} < br>$$This reaction produces hydroxide ions.So the concentration of $\left[\mathrm{OH}^{-}\right]$ increases.The solution becomes basic and its pH rises.There is no increase in $\left[\mathrm{H}^{+}\right]$, and it turns red litmus blue, not blue litmus red.Answer:Option A: an increase in $\left[\mathrm{OH}^{-}\right]$