## finding enthalpy of non-isobaric process

isochoric/isometric: $\Delta V = 0$
isothermal: $\Delta T = 0$
isobaric: $\Delta P = 0$

Sue Bin Park 2I
Posts: 52
Joined: Mon Jun 17, 2019 7:24 am

### finding enthalpy of non-isobaric process

If we are given a non isobaric process, e.g. an irreversible isothermal expansion, how would we find the enthalpy (delta H) of the process? does delta H exist for a non isobaric reaction?

in particular, i'm dealing with a type of question where you open a valve between two containers of gas. I know deltaH = deltaU + P*deltaV, and in isothermal processes, deltaU = 0. does deltaH just equal work? obviously work wouldn't be defined as P*deltaV though, since this is an irreversible process...or is this just a trick question in asking for delta H? lol

Vincent Leong 2B
Posts: 207
Joined: Fri Aug 09, 2019 12:15 am

### Re: finding enthalpy of non-isobaric process

You cant find delta H because enthalpy is heat at constant pressure. To get Delta H you need a constant pressure or else you're solving for q or heat which would be mCdeltaT

VPatankar_2L
Posts: 104
Joined: Thu Jul 25, 2019 12:17 am
Been upvoted: 1 time

### Re: finding enthalpy of non-isobaric process

Delta H only = q at constant pressure, so if the pressure is not constant you won't be able to calculate a value for Delta H