If Δ H is the change in enthalpy and Δ E, the change in internal energy accompanying a gaseous reaction, then

Question

If Δ H is the change in enthalpy and Δ E, the change in internal energy accompanying a gaseous reaction, then (A) Δ H is always greater than Δ E (B) Δ H < Δ E only if the number of moles of the products is greater than the number of moles of the reactants (C) Δ H is always less than Δ E (D) Δ H < Δ E only if the number of moles of products is less than the number of moles of the reactants

Tardigrade Admin · Accepted Answer

As Δ H = Δ E + Δ ng RT if np < nr; Δ ng = np - nr = - ve. Hence Δ H < Δ E.

Q. If $Δ H$ is the change in enthalpy and $Δ E$ , the change in internal energy accompanying a gaseous reaction, then

$Δ H$ is always greater than $Δ E$

$Δ H < Δ E$ only if the number of moles of the products is greater than the number of moles of the reactants

$Δ H$ is always less than $Δ E$

$Δ H < Δ E$ only if the number of moles of products is less than the number of moles of the reactants

As $Δ H = Δ E + Δ n_{g} RT$
if $n_{p} < n_{r}; Δ n_{g} = n_{p} - n_{r} = - v e .$
Hence $Δ H < Δ E .$

Q. If ΔH is the change in enthalpy and ΔE, the change in internal energy accompanying a gaseous reaction, then

ΔH is always greater than ΔE

ΔH<ΔE only if the number of moles of the products is greater than the number of moles of the reactants

ΔH is always less than ΔE

ΔH<ΔE only if the number of moles of products is less than the number of moles of the reactants