Question

Which of the following statements is incorrect?
A. It is not possible to compress a gas at a temperature below \[{{T}_{C}}\]
B. At a temperature below \[{{T}_{C}}\], the molecules are close enough for the attractive forces to act, and condensation occurs.
C. No condensation takes place above \[{{T}_{C}}\]
D. The kinetic energy of the gas molecules is higher above \[{{T}_{C}}\], and the attraction between them decreases.

Answer 1

Hint: Gases can be converted to liquid by compression.in gas the interatomic distance between the gas molecule is very large but when we apply pressure the interatomic distance decreases and the gas becomes liquid. The liquefaction of gas depends upon temperature because above a certain temperature the gas cannot be liquefied because due to temperature the kinetic energy of the gas molecule which made up the gas increases.

Complete step-by-step answer:
The critical temperature is the temperature above which a gas cannot be liquefied no matter how more the pressure is applied. Because above critical temperature the kinetic energy of the gas molecule constituting the gas increases so the kinetic energy of the gas increases. So it is not possible to liquefy a gas above critical temperature so the option A is incorrect.
Below the critical temperature if we apply enough pressure the gas molecule will come closer and the attractive force acts upon the molecule so the liquefaction occurs. So option B is correct.
Above the critical temperature the kinetic energy of the gas molecule constituting the gas is very high and the gas molecule will not condense even if we apply a tremendous amount of pressure. So above the critical temperature no condensation takes place. Sop option C is correct.
Above the critical temperature the gas molecules have higher kinetic energy due to which the attraction between the gas molecules decreases. So option D is correct.

So, the correct answers are “Option A, B and D”.

Note: Critical pressure: It is the pressure required to liquefy a gas at the critical temperature. But above critical temperature a gas cannot be liquefied. The critical temperature of water is $374{}^\circ C$. So above $374{}^\circ C$ water cannot exist in liquid form.
Don’t get confused between gas and vapour. Vapour state is the mixture of two states (liquid + gaseous). But in a gaseous state its only state is gas. No liquid phase is found in a gaseous state.