The equivalent weight of Mohr's salt ${FeSO}_4{\left({NH}_4\right)}_2{SO}_4,6H_{2}O$ is equal to its

Chemical formula of hydrated Mohr's salt is  ${FeSO}_4{\left({NH}_4\right)}_2{SO}_4,6H_{2}O$

$\text{ Equivalent weight }=\frac{\text{ Molar mass }}{\text{ number of electron lost or gained }}$

${Fe}^{+2}\to {Fe}^{+3}$

The oxidation of Fe changes from +2 to +3

So, $\text{ Equivalent weight }=\frac{\text{ Molar mass }}{1}=392.$

Therefore, option A is correct.