Part XII 77. The volume of a sample of air in a cylinder witha movable piston is

Question

Part XII 77. The volume of a sample of air in a cylinder witha movable piston is 2.0 L at a temperature T, as shown in the diagram above. The volume increases to 5.0Las the gas is heated to T, while holding the pressure constant. What effect do the volume and temperature changes have on the average kinetic energy of the molecules in the sample? a) The average kinetic energy increases b) the average kinetic energy decreases c) the average kinetic energy stays the same d) It cannot be determined how the kinetic energy is affected without knowing T, and T 79. The volume of a sample of air in a cylinder with a movable piston is 5.0 L at a temperature T, as shown in the diagram above. The volume decreases to 2.0L as the gas is cooled to T, while holding the pressure constant. What is the ratio T/T? a) 0.40 b) 2.5 c) 10 d) It cannot be determined without knowing the initial pressure 83. The volume of a sample of air in a cylinder with a movable piston is 5.0 L at a pressure P, as shown in the diagram above. The volume decreases to 2.0 L as the temperature is held constant. The air is now at Pa, what is the ratio PJP,? A)0.40 b) 2.5 c) 10 d) It cannot be determined without knowing the initial temperature.

Explanation / Answer

1. average kinetic energy= sqrt(3RT/M)

so since averate kinetic energy is proportional to square root of absolute temperature, as the temperature is increased, averagte kinetic energy increases. ( A is correct).

2. Gas law can be used to detrmined the ratio T2/T1

gas law is P1V1/T1= P2V2/T2

since Pressure is constant, P1=P2

or T2/T1= V2/V1= 2/5= 0.4

3. at constant temperature, P1V1=P2V2, P2/P1= V1/V2= 5/2= 2.5

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