1. The problem statement, all variables and given/known data A rigid tank contains 5 kg of an ideal gas at 4 atm and T=40 deg C. Now, a valve is opened and half of the mass of the gas is allowed to escape. If the final pressure in the tank is 1.5 atm, the final temperature in the tank is? 2. Relevant equations pV=mRT 3. The attempt at a solution I know pV=mRT but I don't know how to use this equation for to different states i.e. beginning and end state.