Question

A gas is liquefied?

• A. Above critical temperature and blow critical pressure.
• B. Below critical temperature and above critical pressure
• C. Below critical temperature and pressure
• D. Above critical temperature and pressure

Answer 1

The correct option is B Below critical temperature and above critical pressure

To convert a gas into liquid we have to just decrease the temperature below critical temprature and increase the pressure applied on that gas. In this way the gas shall change its state from gaseous to liquid and then liquid to solid. But this conversion of state requires very low temperature which is only possible by using heavy machinery.
Similary, reversing the process( increasing the temperature and decreasing the pressure) can revert it back to original.
Liquefaction of a gas occurs when its molecules are pushed closer together. Gas molecules can be squeezed together by one of two methods: by increasing the pressure on the gas or by lowering the temperature of the gas.
In general, gases can be liquefied by one of three general methods:(1) by compressing the gas at temperatures less than its critical temperature; (2) by making the gas do some kind of work against an external force, causing the gas to lose energy and change to the liquid state; and (3) by using the Joule-Thomson effect.
conlusion: hence the answer option(B) is correct.