## Rules for constant pressure

Volume: $\Delta S = nR\ln \frac{V_{2}}{V_{1}}$
Temperature: $\Delta S = nC\ln \frac{T_{2}}{T_{1}}$

Hope Hyland 2D
Posts: 50
Joined: Wed Feb 20, 2019 12:16 am

### Rules for constant pressure

What equations/assumptions do you use when it tells you there is constant pressure? What about constant volume?

Veronica_Lubera_2A
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### Re: Rules for constant pressure

These are just a few but at constant pressure, q=DeltaH and w=-PDeltaV
At constant volume, w=0 and you can evaluate the formulas using this information.

Caitlyn Tran 2E
Posts: 100
Joined: Fri Aug 09, 2019 12:15 am

### Re: Rules for constant pressure

As stated before, in constant pressure, you can assume that $\Delta H = q_{}p$ and $w = -P_{ext}\Delta V$ while in constant volume, you can assume that w = 0 since delta V would be 0. However, you can also use the heat capacity ($C_{p}=\frac{5}{2}R$) for constant pressure and the heat capacity ($C_{v}=\frac{3}{2}R$) for constant volume. Hope this helps!

Jacob Motawakel
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### Re: Rules for constant pressure

At constant pressure, Work = Pressure * Volume, q=Enthalpy, and at constant volume work=0 .

Kayli Choy 2F
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Joined: Sat Aug 24, 2019 12:17 am

### Re: Rules for constant pressure

Additionally, isochoric/isovolumetric/isometric all mean constant volume, isobaric means constant pressure, and isothermal means constant temperature.