Question

If ∆H is the change in enthalpy and ∆E is change in internal
energy accompanying a gaseous reaction, then
(a) ∆H is always greater than ∆E
(b) ∆H < ∆ E only if the number of moles of the products
is greater than the number of moles of the reactants
(c) DH is always less than D E
(d) DH < D E only if the number of moles of products is
less than the number of moles of the reactants.

Answer 1

If ∆H is the change in enthalpy and ∆E is change in internal  energy accompanying a gaseous reaction, then  ΔH < Δ E only if the number of moles of products is  less than the number of moles of the reactants.

- we know that ∆H = ∆E + ∆nRT

-  ∆n = no of gaseous products - no of gaseous reactants

- if products are less than the reactants, only then ∆n is negative

- thus ΔH < ΔE only when the number of moles of products is  less than the number of moles of the reactants

- So the correct option is (d)