Question

A gas can be best liquefied by

• A. Lowering the temperature
• B. Increasing the temperature
• C. Increasing the pressure
• D. Increasing the pressure and lowering the temperature

Answer 1

The correct option is D

Increasing the pressure and lowering the temperature

The explanation for the correct answer
The correct option is (d) Increasing the pressure and lowering the temperature.

• The interparticle distance between the molecules of a gas is very large.
• When pressure is applied to the gas, the interparticle distance starts decreasing resulting in liquefication of gas.
• The molecules of gas have a high value of kinetic energy due to the motion of the molecules of gases.
• When the temperature is decreased the value of kinetic energy also decreases resulting in the liquefaction of gas.

The explanation of incorrect options
Option (a) Lowering the temperature

• Lowering the temperature causes liquefaction of gases, but it is not the sole condition for liquefaction of gases.
• As liquefaction of gases can also be done by increasing the pressure on the gases.

Option (b) Increasing the temperature

• By increasing the temperature of gases, the kinetic energy increases, and liquefaction cannot be obtained.

Option (c) Increasing the pressure

• Increasing the pressure causes liquefaction of gases, but it is not the sole condition for liquefaction of gases.
• As liquefaction of gases can also be done by lowering the temperature.

Therefore, to liquefy gases temperature should be decreased and pressure should be increased, option (D) is the correct answer.