## When to use Cv or Cp? to calculate change in Entropy

isochoric/isometric:
isothermal:
isobaric:

Mirna_Velasco_1L
Posts: 19
Joined: Wed Sep 21, 2016 3:00 pm

### When to use Cv or Cp? to calculate change in Entropy

I understand that we use Cv or Cp when the it states that its either at constant volume or pressure? But if these words are not used, and it just states that its a monatomic ideal gas, which C do use? I noticed that we normally use Cv but why?

Paul Sedaros 1B
Posts: 23
Joined: Fri Sep 25, 2015 3:00 am

### Re: When to use Cv or Cp? to calculate change in Entropy

When we use Cv, it is usually used when there is a change in temperature in the problem

Maria Bajenov 1I
Posts: 28
Joined: Fri Sep 29, 2017 7:06 am

### Re: When to use Cv or Cp? to calculate change in Entropy

It depends on the type of system the reaction is being carried out in. If the problem specifies that it is isothermal, use Cp. It it is being carried out in isochoric, use Cv. If it is isobaric, use Cp to calculate q because pressure is not changing and change in volume will be accounted for in calculating w.

melissa carey 1f
Posts: 53
Joined: Fri Sep 29, 2017 7:06 am

### Re: When to use Cv or Cp? to calculate change in Entropy

Maria Bajenov 1I wrote:It depends on the type of system the reaction is being carried out in. If the problem specifies that it is isothermal, use Cp. It it is being carried out in isochoric, use Cv. If it is isobaric, use Cp to calculate q because pressure is not changing and change in volume will be accounted for in calculating w.

In the isobaric case, how would one find q?