Explanation

The enthalpy is defined by H = E + pV for a change in the states of a system.

ΔH = Δ (E + pV) = ΔE + Δ (pV) = ΔE + pΔV + VΔp 

Enthalpy, H, is a thermodynamic property that describes the heat lost or gained in a system.

The change in enthalpy, ΔH, is equal to the sum of the change in internal energy, ΔU, plus the product of the constant pressure, P, and the change in volume, ΔV.