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 slow enough for the attractive forces to act, and hence 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

The correct option is A It is not possible to compress a gas at a temperature below $T_c$.

The critical temperature $\left(T_c\right)$ of any gas is defined as the temperature above which a gas cannot be liquefied, no matter how much pressure is applied. Gases can only be converted into liquids by compressing it at a suitable temperature and pressure. Gases can be liquefied below the critical temperature because below $T_c$ the molecules are very close to each other as their kinetic energy is very less and particles have significant force of attraction. The liquification of gas become more difficult as the temperature increases because the kinetic energies of the particles also increase.
Hence the options B,C and D are correct stataments and hence incorrect statement is A.