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

The relationship between enthalpy and internal energy change is

Enthalpy change equal internal energy change when

The relationship between enthalpy change (DeltaH) and internal energy change (DeltaE) for a system is given by

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

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

The change in the internal energy of a substance