How are qp and qv different?

isochoric/isometric: $\Delta V = 0$
isothermal: $\Delta T = 0$
isobaric: $\Delta P = 0$

Bryce Barbee
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Joined: Wed Sep 18, 2019 12:20 am

How are qp and qv different?

What is the difference between qc and qv? Do you use both of the as enthalpy in a system?

Jordan Young 2J
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Re: How are qp and qv different?

qp is enthalpy at constant pressure and qv is at constant volume. They are used when finding enthalpy/delta H but also find change in internal energy which is q + w so q can either be qp or qv depending on the given conditions

Abby Soriano 1J
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Joined: Sat Aug 24, 2019 12:16 am

Re: How are qp and qv different?

Jordan Young 2J wrote:qp is enthalpy at constant pressure and qv is at constant volume. They are used when finding enthalpy/delta H but also find change in internal energy which is q + w so q can either be qp or qv depending on the given conditions

I know that qp is another way to describe enthalpy, but can qv also be used? If so could you explain how?

JasonLiu_2J
Posts: 109
Joined: Sat Aug 24, 2019 12:17 am

Re: How are qp and qv different?

qv can also be used to find the enthalpy under the conditions of constant volume. In this scenario, you would need to use the equation ∆H=∆U + ∆PV. Remember that ∆U=q+w, and at constant volume, w=0 (since w=P∆V). As such, you find that ∆U=qv, and the equation for enthalpy change becomes ∆H=qv+V∆P, where volume is a constant and the pressure changes.

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