# Energy under constant pressure and temp

Conceptual problem: let A + 2B -> C + 2D be a reaction under constant pressure P and temp T, that goes all the way towards the products. A,B,C,D are ideal gases. let $\Delta H$ be the molar enthalpy change in the reaction.

What is the change in the internal energy?

The total amount of mols in the reaction is constant throughout it, can we say that $\Delta U=\alpha nR\Delta T$ is the term for the internal energy? (if so that will be 0)

All help appreciated.

as $H=U+PV$ and $PV = n_{tot}RT=const$ throughout the process we get $\Delta(PV)=0 => \Delta U= \Delta H$