Chemical reactions can be either endothermic or exothermic. Hess's Law, Sec. 6.7. State Functions, Sec. You should understand that enthalpy is a state function. In other words is only dependent on the final and initial states, not the pathway between these states.
Volume is another state function.
That is the final volume of a system does not depend on the path that was taken in order to achieve this volume. See page 267. Standard Enthalpies of Formation, Sec. Determining Enthalpies of Reactions, Sec.