Statement-1: Chromium ions give green precipitate of $\mathrm{Cr}(\mathrm{OH}{)}_3$ with ${\mathrm{Na}}_2{\mathrm{CO}}_3$ solution.

Statement-2: $\mathrm{Cr}(\mathrm{OH}{)}_3$ precipitate is slightly soluble in excess of ammonia solution in the cold forming a Violet or pink coloured complex, hexaammine chromium (Ill) ion.

When combined with alkali, ${\left[\mathrm{Cr}{\left({\mathrm{H}}_2\mathrm{O}\right)}_6\right]}^{3+}\left(\mathrm{aq}\right)$ transforms from its original blue-violet colour to a dark green precipitate called $\mathrm{Cr}(\mathrm{OH}{)}_{3\left(\mathrm{s}\right)}$. Precipitate dissolves when there is too much alkali, releasing an aqueous ${\left[\mathrm{Cr}(\mathrm{OH}{)}_6\right]}^{3-}\left(\mathrm{aq}\right)$ complex that is green in colour. This hydroxide,$\mathrm{Cr}(\mathrm{OH}{)}_3$, is an amphoteric substance.

So,statement-1 is True, Statement-2 is True, Statement-2 is NOT a correct explanation for Statement-1.

Hence, option B is correct.