JEE Chemistry 2025 Question with Solution

Given: Two statements about the boiling points of alcohols and phenols.

Find: Which statement is true.

For Statement (I), alcohols and phenols contain the hydroxyl group $-OH$. As the number of carbon atoms increases, molecular size and molecular weight increase, so van der Waals forces also increase. Hence, the boiling points generally increase with increase in the number of carbon atoms.

For Statement (II), alcohols and phenols show intermolecular hydrogen bonding, whereas ethers and haloalkanes do not show such strong hydrogen bonding between their molecules. Because hydrogen bonding is stronger than the intermolecular forces present in ethers and haloalkanes, alcohols and phenols have higher boiling points than these compounds of comparable molecular mass.

Therefore, both Statement (I) and Statement (II) are true. The correct option is D.

Given:

• Statement (I): The boiling points of alcohols and phenols increase with increase in the number of C-atoms.
• Statement (II): The boiling points of alcohols and phenols are higher than ethers and haloalkanes.

Find: The correct option.

1. Alcohols and phenols are characterized by the presence of the hydroxyl group $-OH$.
2. Their boiling points depend strongly on intermolecular forces.
3. With increase in the number of carbon atoms, molecular weight increases.
4. Larger molecules experience stronger van der Waals forces.
5. Therefore, Statement (I) is true.

Now examine Statement (II):

1. Alcohols and phenols can form intermolecular hydrogen bonding.
2. Ethers and haloalkanes lack such strong hydrogen bonding between molecules.
3. Stronger intermolecular attraction means more energy is needed for boiling.
4. Therefore, alcohols and phenols have higher boiling points than ethers and haloalkanes.
5. Hence, Statement (II) is also true.

Therefore, the correct option is D.