# Entropy Change of an Ideal Gas

• Archived

## Homework Statement

Using the expression for the entropy change of an ideal gas when the volume and temperature change and TV$\gamma-1$ = constant, show explicitly that the change in entropy is zero for a quasi-static adiabatic expansion from state V1T1 to state V2T2.

## Homework Equations

TV$\gamma-1$ = constant

dS = dQr / T

## The Attempt at a Solution

My idea was to use T1V1$\gamma-1$ = T2V2$\gamma-1$ and solve for T in terms of V and substitute in to the second equation. I couldn't figure it out from there, so my question is is my idea of what to do fundamentally wrong, or is my calculation once i set up the problem wrong?

## Answers and Replies

Chestermiller
Mentor
$$dS=C_v\frac{dT}{T}+R\frac{dV}{V}$$