The boiling point of water is higher than the boiling point of ethanol because

1. Analyze the question We are asked why water (b.p. 100 °C) boils at a higher temperature than ethanol (b.p. 78 °C). Boiling point depends on the strength of the forces between molecules.

2. The concept Both water and ethanol contain an –OH group, so both form hydrogen bonds between their molecules. The difference is in how strong and how extensive the hydrogen bonding is:

• Water has two hydrogen atoms and two lone pairs on oxygen. Each molecule can form up to 4 hydrogen bonds, which gives a strong 3-D network.
• Ethanol (C₂H₅OH) has only one O–H hydrogen and has a non-polar ethyl group, which gets in the way. Each molecule forms fewer hydrogen bonds, so the overall network is weaker.

More hydrogen bonds per molecule means more energy is needed to separate the molecules, so the boiling point is higher.

3. Check each option

• A. Wrong. Water is covalent, not ionic.
• B. Correct. Both have hydrogen bonding, but in water it is stronger and more extensive.
• C. Wrong. Lattice energy applies to ionic solids, not molecular liquids.
• D. Wrong. Ethanol does have hydrogen bonding, because it has an O–H group.
• E. Wrong. Solvent ability does not determine boiling point.

4. Answer The correct option is B.

5. Exam tip Watch out for the "trap" in option D. Whenever a molecule has an O–H, N–H or H–F bond, it can hydrogen bond. Ethanol therefore does hydrogen bond, and the question is about the degree of hydrogen bonding. The word "stronger" in B is the clue.