Question

1)(Hint: Cp=1.005 kJ/kg-K, Cv=0.718 kJ/kg-K, R=0.287 kJ/kg-K). An air-tight room contains 80 kg of air, and a 2-kW baseboard electric resistance heater in the room is turned on and kept on for 15 min. The temperature rise of air at the end of 15 min is

2)An example of when it is appropriate to model a substance as an ideal gas is when

a. The pressure and temperature are close to the critcal point

b. The pressure and temperature are five times higher than their critical values

c. The pressure and temperature are 100 times higher than their critical values

d. The pressure and temperature are half their critical values

e. the substance is in the vapour state.

3)For ideal gases, the specific heat Cp can be used for a constant-pressure process, and:

a. a constant volume process

b. no other kind of process

c. any process where the change in internal energy is the relevant quantity

d. any process where the change in enthalpy is the relevant quantity

e. any process involving heat transfer (temperature gradient)

4)A room contains 25 kg of air at 100 kPa and 10 degrees C. The room has a 250-W refrigerator (the refrigerator consumes 250 W of electricity when running) and 1-kW electric resistance heater. During a cold winter day, it is observed that both the refrigerator and the resistance heater are running continuously but the air temperature in the room remains constant. The rate of heat loss from the room during that day is

Answer 1