Question

When concentrated sulphuric acid is added to an inorganic mixture containing chloride we get colourless pungent smelling gas HCL but if mixture contains bromide then we get red vapour of bromine. Why?
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Answer 1

When conc. H2SO4 is added to an inorganic mixture containing bromide, initially HBr is produced. HBr, being a strong reducing agent reduces H2SO4 to SO2 with the evolution of red vapour of bromine.

$2NaBrbr + 2H2SO4 → 2NaSO4 + 2HBr \\ 2HBr + 2H2SO4 → Br2 + SO2 + 2H2O \\ \: \: \: \: \ \: \: \: \: \: red \: vapours$

But, when conc. H2SO4 is added to an inorganic mixture containing chloride, a pungent smelling gas (HCl) is evolved. HCl, being a weak reducing agent, cannot reduce H2SO4 to SO2.

2NaCl+2H2SO4----->2NaHSO4+2HCl