Question

Which among the following have the highest boiling point?
A. Hydrogen
B. Helium
C. Neon
D. Xenon
E. Methane

Answer 1

The boiling point of a substance is defined as the temperature at which a liquid starts to boil. Or we can also define it as the temperature at which the vapor pressure of a liquid is equal to the pressure surrounding the liquid.

Complete step by step answer:
The boiling point is that physical property which depends upon the intermolecular force of attraction between the molecules and it is directly proportional to the intermolecular force of attraction that exists between the molecules. i.e the greater the force of attraction between the molecules greater is the boiling point of the substance. The order of the intermolecular force of attraction is given below:
Ionic force > H-bonding > van der-waal force of attraction > dispersion forces.
Since in the above options helium, neon, and xenon all are noble gases, the intermolecular force of attraction that exists between noble gases is known as dispersion forces. It is the weakest force of attraction hence the boiling point of helium, neon, and xenon is the lowest.
The force of attraction that exists in the case of both hydrogen gas and methane is the Vanderwall force of attraction. Since the molecular weight of hydrogen is lower hence the force of attraction in the case of hydrogen is weaker as compared to the force of attraction in the case of methane. Thus the methane has a maximum boiling point in all the options given above.

So, the correct answer is Option E.

Note: The boiling point is an important physical property because we get valuable details about the structure and physical properties of the compounds. It also helps to identify and characterize an organic compound.