JEE Advanced Chemistry: The Halogens and Their Compounds questions with solutions

Q1. Cl2 gas CANNOT be prepared by which of the following methods?

1. Electrolysis of fused NaCl
2. Acidification of bleaching powder
3. Reaction of concentrated HCl with aqueous KMnO4
4. Heating KCl with concentrated H2SO4

Answer: Heating KCl with concentrated H2SO4

Concentrated H2SO4 reacts with KCl by proton transfer to give HCl gas (2KCl + H2SO4 -> K2SO4 + 2HCl). The chloride ion is not oxidised to Cl2 because H2SO4 is not oxidising enough for Cl⁻. All other methods do produce Cl2.