Question

In the brown ring test, the brown colour of the ring is due to

• A. ferrous nitrate
• B. ferric nitrate
• C. a mixture of $NO$ and $NO_2$
• D. nitrosoferrous sulphate

Answer 1

Answer: (D)

nitrosoferrous sulphate

Answer 2

Ring test: To the nitrate salt, add freshly prepared $FeSO _{4}$ solution and then cone $H _{2} SO _{4}$ carefully by the sides of test-tube. A dark brown ring of ferrous nitrososulphate is formed.

$NaNO _{3}+ H _{2} SO _{4} \longrightarrow NaHSO _{4}+ HNO _{3}$
$2 HNO _{3}+6 FeSO _{4}+3 H _{2} SO \longrightarrow 3 Fe _{2}\left( SO _{4}\right)_{3}+2 N O+4 H_{O}$
$FeSO _{4}+ NO \longrightarrow \underset{\text{ferrous nitrososulphate}}{[ Fe \cdot NO ] SO _{4}}$