5 kg of He in a tightly sealed balloon is placed in a big well-insulated house filled with air (with room air being at 1 atm and 25 °C). The He in the balloon, initially at 5 atm at 25 °C, expands so the balloon pressure drops to 1 atm. During the expansion the temperatures of He in the balloon and room air both remain constant at 25°C. The pressure (P [Pa], total volume (Vtotal [m2]), moles of gas (n [mol]) and temperature (T [K]) are related to each other by: PV total/nT =8.314 (J mol-- K-).
(a) If we select He in the balloon as the system, calculate AV, W, Q, and AU for He.
(b) If we select Air in the big house as the system, calculate AV, W, Q, and AU for the Air in the house.
(c) What type of the system for He in the balloon?