It is my understanding that enthalpy differs from internal energy only in that the change in enthalpy takes into account any pressure-volume work done on the system (or by the system) in a reaction, and thus it is equal to the heat transferred to the system, at least in constant pressure.
Many sources say that in a constant pressure, "coffee cup" calorimeter, $q_p = \Delta H$. I understand that. However, they also say that the $q_v$ in a constant-volume calorimeter is equal to the change in internal energy, and not necessarily the change in enthalpy. My thought is that since $\Delta H = \Delta U + P\Delta V$, with $\Delta V$ being zero (it is by definition constant volume), is not $\Delta H = \Delta U = q_v$?