${\mathrm{CrCl}}_3$Solution $+{\mathrm{Na}}_2\mathrm{S}$ Solution$⟶\mathrm{ppt}\left(\mathrm{A}\right)$

The correct formula and colour of A are :

The following reaction is obtained,

${\mathrm{CrCl}}_3\text{ solution }+{\mathrm{Na}}_2\mathrm{S}\text{ solution }\to \mathrm{Cr}(\mathrm{OH}{)}_3\text{, Green }$

Chromium hydroxide $\left(\mathrm{Cr}(\mathrm{OH}{)}_3\right)$  and sodium chloride are produced when chromium chloride $\left({\mathrm{CrCl}}_3\right)$ and NaOH reacts (NaCl). The green precipitate is chromium hydroxide $\mathrm{Cr}(\mathrm{OH}{)}_3$. dissolves in excess NaOH and produces a green-coloured solution.