Enthalpy change equal internal energy change when

Write the expression showing relation between enthalpy change and internal energy change for gaseous phase reaction

For the reaction PCl_(5)(g)toPCl_(3)(g)+Cl_(2)(g) where ΔH and ΔE represents enthalpy change and internal energy change respectively.

For the reaction PCl_(5)(g)toPCl_(3)(g)+Cl_(2)(g) where ΔH and ΔE represents enthalpy change and internal energy change respectively.

In the balanced equation for the combustion of 1 mole of benzoic acid, C6H 5COOH(s) at temp. T, the difference between enthalpy change and internal energy change is equal to

Enthalpy change does NOT equals internal energy change when _______ .

Why heat changes reported are usually enthalpy changes and not internal energy changes?