Critical temperatures for A, B, C and D gases are (25^ ^ C, 10^ ^...

Critical temperature of gas may be defined as that temperature above which it cannot be liquefied how so ever high pressure may be applied on the gas. As we know, (T_C=\frac{8 a}{27 R b}) where $a=$ van der Wal's constant which is a measure of intermolecular forces of attraction. Greater the value of $a$ more easily the gas can be liquefied and hence larger $T_C$ mean larger the value of $a$.