Critical temperature for liquid nitrogen is ?

Ans. is 'c' i.e., -147deg C Critical temperature (Tc) of a substance is the temperature at and above which vapour of that substance can not be liquified, no matter how much pressure is applied (Note : Below critical temprature a substance can exist as a liquid or gas depending on pressure). Critical temperature of N2 is -146.9deg C; that means N2 can be liquified below -146.9deg C --> So, liquid nitrogen must be stored below -146.9deg C.