Question

You are given an inorganic mixture with the information that the cations of group II are absent. However, on passing `H_(2)S` gas through the mixture solution acidified with dilute HCl, yellowish turbidity apperas. Explain.

Answer 1

The mixture probably contains some nitrite or nitrate salt which in the acidic medium releases either nitrous acids or nitric acid. The acid oxidises hydrogen sulphide to sulphur which appears as yellow turbidity.
`2HNO_(2)+H_(2)S to 2NO+2H_(2)O + underset(("Yellow tubidity"))(S)`
`2HNO_(3) +H_(2)S to 2NO_(2)+2H_(2)O + underset(("Yellow turbidity")) (S)`