Question

Why is hydrochloric acid not used for preparation of h2?

Answer 1

You can get hydrogen from hydrochloric acid, but not by trying to split H2 and Cl2 by thermal means. That won’t work. However, you could do something like this:

Fe + 2HCl(a) = FeCl2 + H2(g)

Change in Free Energy: ΔG(20C) = -46.5kJ (negative, so the reaction runs)

Change in Enthalpy: ΔH(20C) = +11.4kJ (positive, so the reaction is endothermic)

However, this strikes me as a difficult and expensive way to get hydrogen. Why not get it from the electrolysis of water?