Liquefaction of gases and critical temperature

Means conversion of gas into liquid by Increasing Pressure and decreasing Temperature

Critical temperature → of a gas is defined as that temperature above which it can’t be liquefied how so over high pressure may be applied on gas.

Critical pressure (P_C) is the P seq. to liquefy the gas at T_C. & critical volume (V_C) is the volume occupied by gas (1 mole) at T_C & P_C

T_C for CO₂ = 30.98°C (PC = 73.9 atm. V_C = 95.6 cm³ mole

T_C = (8a/27Rb), P_C = (a/27b²), V_C = 3b (volume occupied by 1 mole of gas at T_C)

Super critical fluid is any fluid above its critical temperature & pressure.

e.g. CO₂ above 1.1°C & above 600 bar pressure has density about 1 g & its used to dissolve caffeine from coffee beans.

Difference bet. vapour and gas → A gas above T_C is gas & below T_C its vapour.

Importance of T_C→ Increases the value of T_C more easily the gas is liquefied also their value of ‘a’ is also large, ease of liquefaction of fall gases is NH₃ > CO₂ CO > N₂ > H₂ > He

Question:- of T_C for NH₃ = 405.5 k & T_C for CO₂ = 304.10 k which gas will be liquefied easily

Answer:- NH₃