## Cv vs. R

$\Delta G^{\circ}= \Delta H^{\circ} - T \Delta S^{\circ}$

$\Delta G^{\circ}= -RT\ln K$

$\Delta G^{\circ}= \sum \Delta G_{f}^{\circ}(products) - \sum \Delta G_{f}^{\circ}(reactants)$

Rana YT 2L
Posts: 49
Joined: Thu Jul 27, 2017 3:01 am

### Cv vs. R

I was looking through the solutions manual and noticed that it uses Cv and R interchangeably for some problems involving ideal gases. Why can is it that this can happen?

Angel Gomez 1K
Posts: 36
Joined: Fri Sep 29, 2017 7:04 am

### Re: Cv vs. R

When you are measuring the change in heat, or $\Delta H$, of an ideal gas at constant volume, the specific heat will be equal to 3/2 times the ideal gas constant. Here is the equation: $C_{V}=3/2*R$
Therefore, when measuring $\Delta H$, you replace $C_{V}$ with 3/2*R in your $\Delta H=mC_{V}\Delta T$ equation
What you may be seeing instead is replacing C directly with R, and then multiplying the entire equation (or your final answer) with 3/2. This is also valid.