Question

critical temperature for carbon dioxide and methane are 31.1 and -81.9 repectively which of these have stronger intermolecular forces and why?

Answer 1

The critical temperature (it is defined as the temperature above which gas cannot be liquified howsoever high pressure is applied on the gas) of a gas is a measure of the strength of the intermolecular forces of attraction of that gas.
Weaker are the intermolecular forces, more difficult it is to liquify that gas and hence lower would be the critical temperature.
So, CH₄ with low critical temperature, is difficult to liquify and hence weaker are the forces of attraction.
While CO₂ has got high critical temperature, so it has stronger intermolecular forces.