Entropy change for isothermal expansion of ideal gas

[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 :)

 

[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.

 

[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.