Question

Give two chemical tests to distinguish between dilute nitric acid and hydrochloric acid.

Answer 1

Dilute nitric acid	Dilute hydrochloric acid
1. On reacting copper metal with nitric acid brown fumes of nitrogen dioxide. \[\ce{Cu + 4HNO3 -> Cu(NO3)2 + 2NO2 + 2H2O}\]	1.On treating copper metal with HCl We don't observe any reaction.
2. Brown ring test : Nitric acid in a test tube is taken and then and then freshly prepared ferrous sulphate solution is added. Concentrated H2SO4 is then added carefully down the sides of the test tube, dark brown ring is formed at the juctions of two layers. \[\ce{6FeSO4 + 3H2SO4 + 2HNO3 -> 3Fe2(SO4)3 + 2NO + 4H2O }\] \[\ce{FeSO4 + NO + 5H2O -> \underset{\text{Hydrated nitrosoferrous Sulphate (brown ring)}}{[Fe(No)(H2O)5]SO4}}\]	2. No brown ring test is observed in the caseof hydrochloric acid.