deltaS=nCvln(t2/t1) what is Cv?

[Josephine Lu 4L]

what does the Cv mean in the equation deltaS=nCvln(t2/t1) ? what does it stand for, and when should i use it as opposed to deltaS=nRln(V2/v1)?

[Zenita Leang 2K]

Cv is constant volume, which is times the constant R. You use this in deltaS=nCvln(t2/t1) instead of deltaS=nRln(V2/v1) when you have a monatomic ideal gas at constant volume to calculate for entropy.

[Danny Zhang 4L]

Cv is the heat capacity of the system when the volume is constant.

[Emily Kennedy 4L]

where does the 3/2 come from?

[Sheridan Slaterbeck 1J]

when would you use deltaS=nRln(V2/v1) ?

[Kayla Vo 1B]

If the problem gives you temperature and the system is not isothermal, deltaS=nCvln(t2/t1) is used to determine the change in entropy. To calculate the change in entropy of an ideal gas in a reversible isothermal expansion, use deltaS=nRln(V2/V1).

[Linh Vo 2J]

where does the 3/2 come from?

For heat capacities of ideal gases, we use Cv=3/2R for a monoatomic gas and Cv=5/2R for a diatomic gas such as N2 or H2. The constant being multiplied to R is determined by the greater number of degrees of freedom in diatomic as opposed to monoatomic gases, so 5/2 (diatomic) is much bigger than 3/2 (monoatomic).

[Toru Fiberesima 1L]

If a gas is compressed suddenly and irreversibly, treat it as a two step process where the dS from dT and dS from dV need to be accounted for. In this case, you would do dS=nCvln(T2/T1) if v was constant + deltaS=nRln(V2/V1).