Question
Explain with the help of a balanced equation, the brown ring test for nitric acid.
✓
Answer
Brown ring test -
Nitric acid in a test tube is taken and then and then freshly prepared ferrous sulphate solution is added. Concentrated $H _2 SO _4$ is then added carefully down the sides of the test tube, dark brown ring is formed at the junction of two layers.
$
6 FeSO _4+3 H _2 SO _4+2 HNO _3 \longrightarrow 3 Fe _2\left( SO _4\right)_3+2 NO +4 H _2 O
$
$
FeSO _4+ NO +5 H _2 O \longrightarrow \underset{\text { Hydrated nitrosoferrous sulphate(brown ring) }}{\left[ Fe ( NO )\left( H _2 O \right)_5\right] SO _4}
$
Nitric acid in a test tube is taken and then and then freshly prepared ferrous sulphate solution is added. Concentrated $H _2 SO _4$ is then added carefully down the sides of the test tube, dark brown ring is formed at the junction of two layers.
$
6 FeSO _4+3 H _2 SO _4+2 HNO _3 \longrightarrow 3 Fe _2\left( SO _4\right)_3+2 NO +4 H _2 O
$
$
FeSO _4+ NO +5 H _2 O \longrightarrow \underset{\text { Hydrated nitrosoferrous sulphate(brown ring) }}{\left[ Fe ( NO )\left( H _2 O \right)_5\right] SO _4}
$
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