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. Ar
B. CH4
C. H₂O
D. C6H6
Choose the correct option from the following.
Show 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.
- A, B, C and D
- D, C, B and A
- B, C, D and A
- C, D, B and A
The Correct Option is A
Solution and Explanation
The van der Waals constant \( a \) represents the magnitude of intermolecular attractive forces. It increases with molecular size, molecular mass, and the presence of hydrogen bonding. Let us analyze the given gases:
- Argon (Ar): Being a noble gas, Ar has the weakest intermolecular forces and the lowest value of \( a \).
- Methane (\( \text{CH}_4 \)): \( \text{CH}_4 \) has stronger London dispersion forces than Ar due to its larger molecular size.
- Water (\( \text{H}_2\text{O} \)): \( \text{H}_2\text{O} \) has significant hydrogen bonding, increasing its \( a \) value further.
- Benzene (\( \text{C}_6\text{H}_6 \)): \( \text{C}_6\text{H}_6 \) is a large aromatic molecule with strong dispersion forces, giving it the highest \( a \) value among the given gases.
Thus, the increasing order of \( a \) is:
\(Ar (A) < CH_4 (B) < H_2O (C) < C_6H_6 (D) .\)
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