3. The entropy change, ΔS, associated with the isothermal (i.e. constant temperature) change in volume of n moles of an ideal gas from volume V1 to volume V2 is given by the equation ΔS = nR ln(V2/V1) where R is the gas constant.

& If an expansion occurs (V2 > V1) use Equation 1 to deduce whether there will there be an increase or decrease in the entropy of the gas.

If V2>V1, V2/V1>1, so ln(V2/V1)>0, and as n and R are both >0, we have: