## Using Cv,m and Cp,m

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

Charisse Vu 1H
Posts: 101
Joined: Thu Jul 25, 2019 12:17 am

### Using Cv,m and Cp,m

When do we use Cv,m and Cp,m? Also, why and when do we use 5R/2, 3R/2, etc.? I am kind of confused on this, as I don't recall Professor Lavelle really explaining it.

Tyler Angtuaco 1G
Posts: 130
Joined: Wed Sep 11, 2019 12:16 am

### Re: Using Cv,m and Cp,m

The v and p just indicate that it is specific heat at a constant volume or constant pressure. I can't think of a situation where you would need to convert between the two or be extra wary which one the table is giving you. Usually, if you need specific heat, just refer to what the table gives you. You use C=(5/2)R and C=(3/2)R for ideal gases; (5/2)R is for the specific heat of gases at a constant pressure and (3/2)R for constant volume.

Rory Simpson 2F
Posts: 106
Joined: Fri Aug 09, 2019 12:17 am

### Re: Using Cv,m and Cp,m

You would used Cv,m and Cp,m if you want to find Cv or Cp in calculating q (using q=C$\Delta$T). The values using R to calculate C are ways of estimating the heat capacities of certain molecules if you don't know it, but I don't really think he went over that.

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