Delta H and q Interchangeability

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

Delta H and q Interchangeability

Postby Andy Liao 1B » Tue Jan 16, 2018 9:13 pm

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
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Re: Delta H and q Interchangeability

Postby Swetha Sundaram 1E » Tue Jan 16, 2018 11:08 pm

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
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Re: Delta H and q Interchangeability

Postby Erica Nagase 1H » Thu Jan 18, 2018 10:13 am

= 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

Postby Jingyi Li 2C » Thu Jan 18, 2018 10:40 am

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

Postby Clarisse Wikstrom 1H » Thu Jan 18, 2018 10:50 am

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
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Joined: Fri Sep 29, 2017 7:04 am

Re: Delta H and q Interchangeability

Postby Justin Chang 2K » Thu Jan 18, 2018 3:23 pm

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.


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