Delta H and Delta U

[Mary Becerra 2D]

Why can we equate delta H (heat transfer at constant pressure) and delta U (heat transfer at constant volume)?

[Sarah_Stay_1D]

Why can we equate delta H (heat transfer at constant pressure) and delta U (heat transfer at constant volume)?

You can not always equate delta H (enthalpy) to delta U (internal energy). The two are only equal when you have constant pressure and constant volume. This is true because at constant pressure ΔH = ΔU + PΔV. So, if the volume is constant, the change in volume would be 0. Therefore, ΔH = ΔU + P(0) so, ΔH =ΔU.

[204918982]

Yes this is only true when the pressure and volume are constant

[Wayland Leung]

How are the equations for delta h and delta u different? Are there differenet variables in each equation?