Enthalpy formula from day 1

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Anika_Patel_1G
Posts: 32
Joined: Fri Sep 29, 2017 7:06 am

Enthalpy formula from day 1

Postby Anika_Patel_1G » Fri Jan 12, 2018 4:02 pm

Why does delta H = qp at constant pressure? I know we were told to memorize this, but I don't understand where it came from.

Cynthia Tsang
Posts: 52
Joined: Fri Sep 29, 2017 7:07 am
Been upvoted: 1 time

Re: Enthalpy formula from day 1

Postby Cynthia Tsang » Fri Jan 12, 2018 4:08 pm

Because the pressure is not changing, none of the heat being released is going into the surroundings. This would make the change a closed system and all of the heat released in a reaction would equal the enthalpy of the reaction.

Sirajbir Sodhi 2K
Posts: 47
Joined: Sat Jul 22, 2017 3:00 am

Re: Enthalpy formula from day 1

Postby Sirajbir Sodhi 2K » Fri Jan 12, 2018 9:16 pm

I'm pretty sure enthalpy is really just a convention created by scientists to make calculations convenient (most reactions occur at constant pressure). It is really hard to explain the equations related to enthalpy from a conceptual standpoint. This one can be derived, but it requires the First Law of Thermo and some relatively difficult math.


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