## Enthalpy formula from day 1

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

### Enthalpy formula from day 1

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

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

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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