Question

Assertion: Copper does not react with dilute sulphuric acid, liberating hydrogen.
Reason: Copper is lower in reactivity series than hydrogen, or more fundamentally, because the magnitude of change in Gibbs free energy when a single atom of elemental hydrogen ionizes is greater than the magnitude of the change in Gibbs free energy when a single atom of elemental copper ionizes.
A.Both assertion and reason are correct and reason is the correct explanation for assertion.
B.Both assertion and reason are correct but reason is not the correct explanation for assertion.
C.Assertion is correct but reason is incorrect
D.Both assertion and reason are incorrect

Answer 1

Hint: First we must find out if copper reacts with dilute sulphuric acid or not. The reduction potential of copper is high and the oxidation potential of copper has a negative value. In the reactivity series, copper is placed below hydrogen.

Complete step by step solution: We know that copper does not react with dilute sulphuric acid. Dilute sulphuric acid, dilute nitric acid are non-oxidising acids.
Copper does not react with dilute sulphuric acid. This is because copper is lower in reactivity series than hydrogen. Copper has higher reduction potential than that of hydrogen.
Also, the magnitude of change in Gibbs free energy when a single atom of elemental hydrogen ionizes is greater than the magnitude of the change in Gibbs free energy when a single atom of elemental copper ionizes.
Thus, copper cannot displace hydrogen from the non-oxidising acid. The chemical potential of copper is insufficient to liberate elemental hydrogen from the compound in which the oxidation state of hydrogen is +1.
Thus, copper does not react with dilute sulphuric acid, liberating hydrogen.
Thus, both assertion and reason are correct and reason is the correct explanation for assertion.

Thus, the correct option is (A) both assertion and reason are correct and reason is the correct explanation for assertion.

Note: When copper reacts with concentrated sulphuric acid, the concentrated sulphuric acid gets reduced and the copper metal gets oxidised. The concentrated sulphuric acid gets reduced to sulphur dioxide and the copper metal gets oxidised to copper sulphate in which the copper ion has a charge +2. Water is liberated in the reaction.
The reaction of copper metal with concentrated sulphuric acid is as follows:
${\text{Cu}} + 2{{\text{H}}_2}{\text{S}}{{\text{O}}_4} \to {\text{CuS}}{{\text{O}}_4} + {\text{S}}{{\text{O}}_4} + {\text{2}}{{\text{H}}_2}{\text{O}}$