Gas Laws Revision

An ideal gas undergoes an isobaric expansion followed by an isochoric cooling. Which of the following statements must be true after the completion of these processes?

• The final pressure is less than the original pressure.

• The final volume is less than the original volume.

• The final temperature is less than the original temperature.

• The total quantity of heat, Q, associated with these processes is positive.

A certain quantity of an ideal gas initially at temperature T₀, pressure p₀, and volume V₀ is compressed to one-half its initial volume. As shown above, the process may be adiabatic (process 1), isothermal (process 2), or isobaric (process 3).

Which of the following is true of the final temperature of this gas?

• It is greatest for process 1.

• It is greatest for process 2.

• It is greatest for process 3.

• It is the same for all three processes.

Absolute zero is best described as that temperature at which

• water freezes at standard pressure.

• the molecules of a substance have maximum kinetic energy.

• the molecules of a substance have maximum potential energy.

• the molecules of a substance have minimum kinetic energy.

A sample of an ideal gas is in a tank of constant volume. The sample absorbs heat energy so that its temperature changes from 300 K to 600 K. If v₁ is the average speed of the gas molecules before the absorption of heat and v₂ is their average speed after the absorption of heat, what is the ratio v₂/v₁?

• 4

• 2

• 2^1/2

• 1/2

The graph below shows the variation of the pressure p with volume V of an ideal gas during one cycle of an engine.

Which of the following correctly names the thermodynamic process associated with the parts Y→Z and Z→X of the cycle?

• A

• B

• C

• D

The pressure exerted by an ideal gas, maintained at a constant temperature, is inversely proportional to the volume occupied by the gas.

Which of the following statements is not true?

• The average molecular kinetic energy remains constant.

• The gas must consist of identical molecules.

• The mass of gas is fixed.

• The number of molecules in the gas doesn’t change.

The sample of an ideal gas at 27^oC is placed in a sealed container. The gas is heated at constant volume to a temperature of 324 ^oC.

The ratio of the final pressure to the initial pressure exerted by the gas is approximately

• 1

• 2

• 4

• 12

The absolute temperature scale is a theoretical scale proposed by Lord Kelvin. On this scale, zero is the temperature at which

• all gases become liquids

• an ideal gas would exert no pressure

• the Celsius temperature is -373^oC

• water freezes

The graph shows the variation with absolute temperature T of the pressure p of a fixed mass of an ideal gas.

Which of the following is correct concerning the volume and the density of the gas?

• A

• B

• C

• D