please answer number 2

1. We start with a mole of monatomic ideal gas at a pressure of P=1atm and a temperature of T=398K, confined in a cylinder under a movable piston. What is its final state (i.e., volume and temperature) after it undergoes a reversible adiabatic expansion to a pressure of Pf=0.5atm ? What is its entropy change? 2. Start with the same system in the same initial state, also adiabatically sealed, but now we drop the external pressure suddenly to Pf=0.5atm. What is the state of the system (i.e., volume and temperature) after it comes to equilibrium at this new pressure? What is its entropy change