# Would the change in enthalpy change of chemical reaction in space be considered as change in internel enrgy?

The formula of enthalpy change is

change in H = U + P*(change in V)

In space since there is no air, thus atmospheric pressure = 0 , P= 0 , Pv = 0 ,

So will H = U ?

• Yes. Then again, every compound has a vapor pressure, so in the equilibrium (given $P=0$) they all will up and evaporate, leaving you with a pretty dull environment. – Ivan Neretin Jun 6 '18 at 13:20