A pale green crystalline inorganic salt (A) dissolves freely in water. It gives a brown precipitate on addition of aqueous $NaOH$ The solution of (A) also gives a black precipitate on bubbling $H_{2}S$ in alkaline medium. An aqueous solution of (A) decolourises the pink colour of the permanganate solution. The metal in the salt solution is :

Pale green crystalline metal salt is ferrous sulphate. It dissolves freely in water on standing it gives a brown ppt of basic ferric sulphate $4{\mathrm{FeSO}}_4+2{\mathrm{H}}_2\mathrm{O}+{\mathrm{O}}_2\to 4\mathrm{Fe}\left(\mathrm{OH}\right)(\mathrm{SO}{)}_4$ The metal salt solution also gives a black ppt on bubbling  $H_{2}S$ in basic medium. An aqueous solution of the metal salt decolorizes the pink colour of the permanganate solution 

$2{\mathrm{KMNO}}_4+8{\mathrm{H}}_2{\mathrm{SO}}_4+10{\mathrm{FeSO}}_4\to {\mathrm{K}}_2{\mathrm{SO}}_4+2{\mathrm{MnSO}}_4+5{\mathrm{Fe}}_2{\left({\mathrm{SO}}_4\right)}_3+8{\mathrm{H}}_2\mathrm{O}$