JEE Main 2023 — d and f Block Elements Question with Solution

The formula for ferrous ammonium sulphate is ${\mathrm{FeSO}}_4.({\mathrm{NH}}_4{)}_2{\mathrm{SO}}_4.6{\mathrm{H}}_2\mathrm{O}$. It is prepared by dissolving equimolar mixture of hydrated ferrous sulphate and ammonium sulphate in water containing a little sulphuric acid. The solution is subjected to crystallisation, ferrous ammonium sulphate separates out from the solution.

The chemical reaction is given below.

${\mathrm{FeSO}}_4 + ({\mathrm{NH}}_4{)}_2{\mathrm{SO}}_4 + 6{\mathrm{H}}_2\mathrm{O} \to {\mathrm{FeSO}}_4.({\mathrm{NH}}_4{)}_2{\mathrm{SO}}_4.6{\mathrm{H}}_2\mathrm{O} (\mathrm{Mohr}’\mathrm{s} \mathrm{salt})$

Avoid prolonged heating while preparing crystals of ferrous ammonium sulphate, as it may oxidise ferrous ions to ferric ions and change the stoichiometry of the crystals.