Entropy Change of an expanding gas

1. May 22, 2008

cmcc3119

Two moles of an ideal gas undergo a reversible isothermal expansion from 1.97×10−2 m^3 to 4.82×10−2 m^3 at a temperature of 20.0 C.

What is the change in entropy of the gas?

WORKING:

Using $$\Delta$$S = nRIn(V2/V1)

= 2(8.31*ln(4.82*10^-2/1.97*10^-2)

ANS = -138.20 J/K

Is this correct? I can only enter it once on my website and I want to make sure this is right first time :)

Last edited: May 22, 2008
2. May 22, 2008

alphysicist

Hi cmcc3119,

I think you made a math error in your calculation; I don't think that number follows from the line above it.

3. May 22, 2008

cmcc3119

Yep I figured out the right anwer which is 14.9

I don't know what I meant with that massive negative figure! Thanks for you help anyway.