A well insulated air storage tank initially contains N moles of pressurized air at temperature T and pressure P. If the release valve is opened the air is allowed to escape into a vacuum system. Derive an expression for the instantaneous temperature in the tank as a function of the number of moles N of air remaining in the tank at any given moment. You may assume the gas behaves ideally and that the heat capacity of the gas is independent of temperature. What is the predicted temperature if the tank is fully evacuated ? Calculate it

Please help me derive the expression and calculate temp if tank is fully evacuated and please show all work to help me solve.