Question

Lead is not used in preparation of h2 gas using dil acid why

Answer 1

Lead is above hydrogen in the metal activity series ( H2 is included for comparison of reactivity with other metals). So it can displace H from compounds.

In the reactions with acids, insoluble salts of lead are produced which forms a coating on pure lead and prevents the reaction from proceeding further. Thus, Pb is not used to prepare H2.