Statement I: When a haloalkane dissolves in water, the new attractions set up between the haloalkane and water molecules are stronger than the original hydrogen bonds in water.
Statement II: Haloalkanes tend to dissolve in organic solvents because the new intermolecular attractions between haloalkane and solvent molecules have much the same strength as the ones being broken.
In the light of the above statements, choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Only Statement II is correct.
A substance dissolves well when the energy released by the new attractions formed is about the same as the energy needed to break the old attractions.
Statement I: When a haloalkane dissolves in water, the new attractions set up between the haloalkane and water molecules are stronger than the original hydrogen bonds in water. — False. The new attractions are not as strong as the hydrogen bonds between water molecules, so less energy is released than is used. This is why haloalkanes are only very slightly soluble in water.
Statement II: Haloalkanes tend to dissolve in organic solvents because the new intermolecular attractions between haloalkane and solvent molecules have much the same strength as the ones being broken. — True. The energy taken and the energy given back are nearly equal, so haloalkanes dissolve in organic solvents.
NCERT (2026-27 edition):
6.6 Physical Properties – “The haloalkanes are very slightly soluble in water. In order to dissolve haloalkane in water, energy is required to overcome the attractions between the haloalkane molecules and break the hydrogen bonds between water molecules. Less energy is released when new attractions are set up between the haloalkane and the water molecules as these are not as strong as the original hydrogen bonds in water. As a result, the solubility of haloalkanes in water is low. However, haloalkanes tend to dissolve in organic solvents because the new intermolecular attractions between haloalkanes and solvent molecules have much the same strength as the ones being broken in the separate haloalkane and solvent molecules.”