Q: Critical temperature of CO2 is 31.2 °C . In summer , the room temperature is 40 °C , then
(a) CO2 cannot be liquefied
(b) CO2 can be liquefied with increase of pressure
(c) CO2 can be liquefied with decrease of pressure .
(d) CO2 cannot be liquefied if temperature of CO2 is decreased below 31.2 °C
Sol: Gases cannot be liquefied above critical temperature . But by increasing pressure CO2 can be liquefied .