Elements of Groups 16, 17 and 18 — Chemistry STD 12 Science — Question

(c): On treating aqueous solution of nitrate salt with freshly prepared solution of ferrous sulphate and concentrated sulphuric acid, a brown ring at the junction of two liquids is formed.
$
NaNO _3+ H _2 SO _4 \rightarrow NaHSO _4+ HNO _3
$
Salt
$6 \mathrm{FeSO}_4+2 \mathrm{HNO}_3+3 \mathrm{H}_2 \mathrm{SO}_4 \rightarrow 3 \mathrm{Fe}_2\left(\mathrm{SO}_4\right)_3+4 \mathrm{H}_2 \mathrm{O}+2 \mathrm{NO}$

$\left[\mathrm{Fe}\left(\mathrm{H}_2 \mathrm{O}\right)_6\right] \mathrm{SO}_4+\mathrm{NO} \rightarrow\left[\mathrm{Fe}\left(\mathrm{H}_2 \mathrm{O}\right)_5 \mathrm{NO}_3 \mathrm{SO}_4+2 \mathrm{H}_2 \mathrm{O}\right.$
$\quad$

Ferrous sulphate $\quad$$\quad$$\quad$$\quad$$\quad$ Brown ring