Which of the following has the highest critical temperature?

H2

N2

NH3

H2O

The correct answer is H2O

Explanation:

Critical Temperature is the temperature of a substance in its critical state which is the highest temperature at which it is possible to separate substances into two fluid phases (vapor and liquid). At higher temperatures, the gas cannot be liquefied by pressure alone. In the given options water has the highest value of critical temperature as compared to the other given compounds which are H2 = - 240 °C, N2 = - 147 °C and NH3 = 132.4 °C.