1. The problem statement, all variables and given/known data Two moles of an ideal mono atomic gas (C2=12. 55 JK-1mol-1) expands irreversibly and adiabatically from an initial pressure of 10 atm against a constant external pressure of 1 atm until the temperature drops from the initial value of 325 K to a final temperature of 275 K. Calculate the work done by the gas and its final volume. 2. Relevant equations W=-Pext[Vf-Vi]---(1) PV=nRT -----(2) 3. The attempt at a solution work done can be found easily W=-pext (ΔV) =-1255 J And V 1 can be found by the ideal gas equation. BUT, there are two ways to find V2 : that is by ideal gas equation and by the work equation ( by putting the value of V 1 in it ). Both these method give different values of final volume. Which method is wrong here? And why?