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### q and delta H

Posted: Sat Mar 16, 2019 10:32 pm
Hello, I was wonder if q and delta H are the same thing? Because I see them being use interchangeably.

### Re: q and delta H

Posted: Sat Mar 16, 2019 10:37 pm
I think q = delta H under constant pressure. I also think that delta H implies constant pressure already so they can be used interchangeably but I am not sure.

### Re: q and delta H

Posted: Sat Mar 16, 2019 10:42 pm
q is equal to delta H when pressure is constant.

This gives you:

delta U = delta H - P(delta V)

### Re: q and delta H

Posted: Sat Mar 16, 2019 10:43 pm
They can be used interchangeably

### Re: q and delta H

Posted: Sat Mar 16, 2019 10:43 pm
the definition of enthalpy is the change in heat of a system at constant pressure. so q = deltaH at constant pressure.

### Re: q and delta H

Posted: Sat Mar 16, 2019 11:24 pm
delta H = delta U + P delta V

when there is a constant pressure,

delta H= q

I think the q comes from the delta U (as delta U= q +w)

Hope this helps.

### Re: q and delta H

Posted: Sun Mar 17, 2019 3:13 pm
So Delta U = q + w = q - PdeltaV, meaning that under constant pressure U = q = delta H. This is where most of the interchangeability comes from as systems with constant pressure appear often in our problems.