[hardman]

I am unsure on how to calculate the change in molar entropy from the little information i ahve been given in a question.

The question is: Calculate the change in molar entropy when carbon dioxide expands isothermally from 1.5dm^3 to 4.5dm^3.

I think i have to use the equation:

dS= nRln V1 + V2/V1

but how would i calculate n from the information given?

[tamim83]

The equation you want to use is

deltaS = nRln(V_f/V_i)

You can use 1 mole for n (I suppose) and R in whatever units you are asked to use.  From there, it is just plug and chug.