## Delta H and q Interchangeability

Andy Liao 1B
Posts: 52
Joined: Thu Jul 13, 2017 3:00 am

### Delta H and q Interchangeability

I was wondering if delta H and q are ever interchangeable. Are there certain circumstances that allow for them to be? Can someone please explain? Sometimes in the solutions manual, delta H is used instead of q, like for example, in problems 8.37 and 8.45.

Swetha Sundaram 1E
Posts: 59
Joined: Fri Sep 29, 2017 7:04 am
Been upvoted: 1 time

### Re: Delta H and q Interchangeability

I think Delta H is only equal to q with a subscript "p" because the pressure has to remain constant for the equation to hold

Erica Nagase 1H
Posts: 30
Joined: Sat Jul 22, 2017 3:00 am

### Re: Delta H and q Interchangeability

$\Delta H$ = q (heat) at a constant pressure

Jingyi Li 2C
Posts: 56
Joined: Fri Sep 29, 2017 7:06 am

### Re: Delta H and q Interchangeability

delta H only equals to q at constant pressure.

Clarisse Wikstrom 1H
Posts: 63
Joined: Fri Sep 29, 2017 7:05 am

### Re: Delta H and q Interchangeability

This is why sometimes Lavelle will write qp instead of q, indicating it is at constant pressure and is interchangeable with deltaH.

Justin Chang 2K
Posts: 53
Joined: Fri Sep 29, 2017 7:04 am

### Re: Delta H and q Interchangeability

Yeah, the definition of enthalpy is the heat absorbed or released at a constant pressure. q with a subscript p means the heat absorbed or released at a constant pressure, so the two are interchangeable. If there is no subscript p after the q, however, then the two are not interchangeable.