Question

Critical temperature for carbon dioxide and methane are ${31.1^o}C$ and $ - {81.9^o}C$ respectively. Which of these has stronger intermolecular forces and why?

Answer 1

Hint: Carbon dioxide also known as dry ice in its solid state is a colourless gas with chemical formula $C{O_2}$. Whereas methane is the simplest alkane and a group-14 hydride with chemical formula $C{H_4}$.
$C{H_4}$ is the main constituent of the natural gas.

Complete answer
The highest temperature at which any element or compound exists in its liquid form is known as the critical temperature of that substance. At the temperature greater than the critical temperature, the substance exists in its gaseous form. Also, we know that the liquefaction of the gas becomes easier with the higher critical temperature. That means as the temperature increases it becomes easier to liquefy the gas.
Intermolecular forces are the forces of attraction between the particles of a substance that tend to attract the particles together. The van der Waals forces and induced-dipole forces are the examples of intermolecular forces. Also, we know that the critical temperature is directly proportional to the intermolecular forces. This is because the substances which have strong intermolecular forces generally tend to form a liquid at a very large temperature range.
As per the information given in the question the critical temperature of carbon dioxide is ${31.1^o}C$ whereas the critical temperature of methane is $ - {81.9^o}C$. Since the intermolecular forces are directly proportional to the critical temperature, so carbon dioxide will have stronger intermolecular forces as the critical temperature of carbon dioxide is greater than methane.

Hence, carbon dioxide has the stronger intermolecular forces of attraction.

Note:
Thus, from the given information it is clear that carbon dioxide has a greater critical temperature than methane, so it will also possess stronger intermolecular forces of attraction between the particles. It is due to the relationship of direct proportionality between the critical temperature and the intermolecular forces that states that greater the critical temperature of a substance means stronger will be the intermolecular forces of attraction between its particles.