Reactions of the halide ions with concentrated sulphuric acid

acid base reaction trend

NaX (s) + H2SO4 (l) - NaHSO4 (aq) + HX (g)

redox reaction trend

2HX (g) + H2SO4 (l) - X2 (g) + SO2 (g) + 2H2O (l)

Iodine further redox reaction

6HI (g) + H2SO4 (l) - 3I2 (g) + S (s) + 4H2O (l)

8HI (g) + H2SO4 (l) - 4I2 (g) + H2S (g) + 4H2O (l)

Bromine redox reaction identification

orange/brown gas

Iodine redox reaction identification

SO2 - purple gas

S - yellow solid or powder

H2S - rotten gas smell