Question

Identify only the anion present in the following compound:

The solution of the compound which on treating with concentrated sulphuric acid and freshly prepared ferrous sulphate solution produces a brown ring.

Answer 1

The anion present is nitrate \[\ce{NO3-}\]. The nitrate-containing chemical undergoes the following reactions to generate a brown ring.

\[\ce{NO^{-}_3 + H2SO4 -> HNO3 + HSO^{-}_4}\]

\[\ce{2HNO3 -> H2O + 2NO + 3[O]}\]

\[\ce{FeSO4 + NO + 5H2O -> \underset{(Brown ring)}{[Fe(H2O)5NO] SO4}}\]