1. The problem statement, all variables and given/known data The van der Waals’ equation of state for one mole of gas is given by (P+a/V2)(V-b)=RT where V is the molar volume at temperature T, and a and b are constants. The internal energy of the gas is given by E=(3/2)RT-a/V Initially, one mole of the gas is at a temperature T1 and occupies a volume V1. The gas is allowed to expand adiabatically into a vacuum so that it occupies a total volume V2. What is the final temperature of the gas? 2. Relevant equations 3. The attempt at a solution I guess the energy of the gas is constant as it is an adiabatic expansion(right?..). So E1=E1 and so T2=T1+2a/(3R)(1/V2-1/V1) Do I need the first equation provided?