Deck 3: Properties of Pure Substances

Question 1

A rigid tank contains 7 kg of an ideal gas at 5 atm and 30°C. Now a valve is opened, and half of mass of the gas is allowed to escape. If the final pressure in the tank is 1.5 atm, the final temperature in the tank is

A)-91°C
B)18°C
C)-182°C
D)91°C
E)15°C

Answer 1

-91°C

Question 2

The pressure in an air storage tank is measured to be 250 kPa (gage) in the morning, and 275 kPa (gage) in the afternoon as a result of solar heating. The local atmospheric pressure is 100 kPa. If the temperature of air in the tank is 15°C in the morning, the air temperature in the afternoon is

A)15.9°C
B)31.5°C
C)38.0°C
D)16.2°C
E)15°C

Answer 2

31.5°C

Question 3

A 230-m³ rigid tank is filled with saturated liquid-vapor mixture of water at 120°C. If 25% of the mass is liquid and the 75% of the mass is vapor, the total mass in the tank is

A)252 kg
B)824 kg
C)344 kg
D)230 kg
E)683 kg

Answer 3

344 kg

Question 4

Water is boiled at 300 kPa pressure in a pressure cooker. The cooker initially contains 3 kg of water. Once boiling started, it is observed that half of the water in the cooker evaporated in 30 minutes. If the heat loss from the cooker is negligible, the average rate of energy transfer to the cooker is

A)2.3 kW
B)136 kW
C)3.6 kW
D)1.80 kW
E)0.9 kW

Question 5

A 0.2-m³ rigid tank contains 8 kg of water (in any phase or phases) at 500 kPa. The temperature in the tank is

A)27°C
B)102°C
C)381°C
D)246°C
E)152°C

Question 6

Water is boiling at a temperature of 95°C in a pan. If heat is transferred to the pan at a rate of 2 kW, the amount of water that evaporates in 30 minutes is

A)1. 6 kg
B)1.4 kg
C)9.0 kg
D)0.022 kg
E)0.87 kg

Question 7

Water is boiled in a pan on a stove at sea level. During 15 min of boiling, it is observed that 150 g of water has evaporated. Then the rate of heat transfer to the water is

A)26.8 kJ/min
B)22.6 kJ/min
C)0.45 kJ/min
D)4.2 kJ/min
E)16.9 kJ/min

Question 8

A 6-kg brass ball whose specific heat is 0.40 kJ/kg.°C is brought in to a room filled with saturated steam at 90°C. The temperature of the ball rises from 20°C to 90°C while some steam condenses on the ball as it loses heat (but it still remains at 90°C). The mass of steam that condensed during this process is

A)63 g
B)574 g
C)74 g
D)446 g
E)217 g

Question 9

A rigid tank contains 0.8 kg of steam at 10 MPa and 300°C. The volume of the tank is

A)11 m³
B)21 m³
C)4.3 m³
D)1.1 m³
E)0.23 m³

Question 10

Consider a sealed can that is filled with refrigerant-134a at 20°C. Now a leak develops, and the pressure in the can drops to the local atmospheric pressure of 80 kPa. The temperature of the refrigerant in the can is expected to drop to (rounded to the nearest integer)

A)0°C
B)-31°C
C)-18°C
D)3°C
E)20°C