# Liquefaction of Gas

Liquefication of gas is the process of converting gas into a liquid state. This process includes a number of phases and it is used for scientific, commercial and industrial purpose.

Liquefaction can also be used for finding the fundamental properties of gas molecules.

Questions:

1. Collision frequency (Z) of a gas at a particular pressure:

(a)    decreases with the increase of temperature

(b)   increases with increase of temperature

(c)    decreases initially and later on increases

(d)   increases initially and decreases later on

2. If the collision frequency of a gas at 1 bar pressure is Z, then its collision frequency at 0.5 bar is:

(a)    1.0 Z

(b)   0.25 Z

(c)    1.25 Z

(d)   0.56 Z

3. Which has the longest mean free path?

(a)    Oxygen $(O_2)$

(b)   Nitrogen $(N_2)$

(c)    Hydrogen $(H_2)$

(d)   $CH_4$

4. When a compressed gas is allowed to expand through a porous plug at a temperature above its inversion temperature, then:

(a)    a decrease in temperature is observed

(b)   an increase in temperature is observed

(c)    temperature increases after an initial fall in temperature

(d)   no change in temperature

5. Liquefaction of gases can be achieved by:

(a)    cooling

(b)   compressing the gas above critical temperature

(c)    compressing the gas below critical temperature

(d)   all of the above