Question

Arrange the following gases in increasing order of van der Waals constant 'a'
A. Ar
B. CH4
C. H₂O
D. C6H6
Choose the correct option from the following.

• A. A, B, C and D
• B. D, C, B and A
• C. B, C, D and A
• D. C, D, B and A

Hint:

Van der Waals constant a is proportional to the strength of intermolecular forces. Hy drogen bonding and larger molecular size significantly increase the value of a.

Answer 1

The Correct Option is A

To determine the increasing order of the van der Waals constant 'a' for the gases Ar, CH₄, H₂O, and C₆H₆, we need to understand the significance of the van der Waals constant 'a'.

The van der Waals constant 'a' is a measure of the magnitude of attractive forces between gas molecules. The higher the value of 'a', the stronger the intermolecular attractions between the molecules of the gas.

Step-by-step reasoning:

1. Argon (Ar): It is a noble gas with no dipole moment or significant intermolecular forces. As such, it has the lowest 'a' value among the given options.
2. Methane (CH₄): It is a small non-polar molecule with weak Van der Waals forces.
3. Water (H₂O): It is a polar molecule, capable of hydrogen bonding, so it has a relatively higher 'a' value compared to Ar and CH₄.
4. Benzene (C₆H₆): Being a larger molecule with the ability to have π-π stacking interactions, it has the highest value of 'a'.

Thus, their increasing order of van der Waals constant 'a' is:

A. Ar < B. CH₄ < C. H₂O < D. C₆H₆

The correct option is: A, B, C and D