3) A rigid tank of volume 0.5 m³ is initially evacuated. A tiny hole develops in the wall, and air from the surroundings at 1 bar, 21°C leaks in. Eventually, pressure in the tank reaches 1 bar. The process occurs slowly enough that heat transfer between the tank and the surroundings keeps the temperature of the air the tank constant at 21°C. Determine the amount of transfer, in kJ. 4) Consider filling a gas cylinder with ethane from a high-pressure supply line. Before filling, the cylinder is empty (vacuum). The valve is then opened, exposing the tank to a 3-MPa line at 500 K until the pressure of the cylinder reaches 3 MPa. The valve is then closed. The volume of the cylinder is 50 L. For ethane, use Van der Waals equation of state: a) What is the temperature immediately after the valve is closed? b) If the cylinder then sits in storage at 293 K for a long time, what is the entropy change of the universe (from the original, unfilled state)? c) Repeat part a and b by assuming ethane behaves as an ideal gas. d) Repeat part a and b by assuming the filling compound is steam and using steam tables.