Which of the following are the most favorable conditions for liquefying a gas?

Q. Which of the following are the most favorable conditions for liquefying a gas?

1. Low pressure and high temperature
2. Low pressure and low temperature
3. High pressure and high temperature
4. High pressure and low temperature

Answer: High pressure and low temperature

High pressure and low temperature are the most favorable conditions for liquefying a gas.

Liquefaction of gases is a physical conversion of a gas into a liquid state (condensation).

Condensation is the process through which gas changes into a liquid when it touches a cooler surface. Condensation is an important part of the water cycle. It is the opposite of evaporation.

The liquefaction of gases is a complicated process that uses various compressions and expansions to achieve high pressures and very low temperatures, using, for example, turboexpanders.
The two necessary conditions for liquefaction of gases are:

1. By increasing the pressure
2. By reducing the temperature.

When high pressure is applied to a gas, it gets compressed and when we lower its temperature it gets cooled.

Ammonia gas can be liquefied by applying high pressure and lowering the temperature.