Question

Give reason for the following :

(a) Though lead is above hydrogen in the activity series, it does not react with dilute hydrochloric acid or dilute sulphuric acid.

(b) Potassium and sodium are not used fro reaction with dilute hydrochloric acid or dilute sulphuric acid in laboratory preparation of hydrogen.

Answer 1

(a) Because the product, I.e. the chloride/ sulphate formed by such a reaction is insoluble, and stops any further reaction due to an insoluble coating.

(b) Potassium, sodium, lithium and calcium all react violently
with dilute sulfuric acid and dilute hydrochloric acid.
It is dangerous to put thesemetals into an acid.
The reaction is similar to the reaction with water,
forming the metal salt (either sulfate or chloride) plus H2(g).