Most alkanes are insoluble in water because they are what?

• A. Non-polar
• B. Polar
• C. Ionic
• D. Hydrophilic

Answer: (A)

Solubility in water depends on polarity and the ability to form intermolecular forces with water. Water is a polar molecule that forms strong hydrogen bonds, so substances that are also polar or ionic tend to dissolve because they can engage in dipole-dipole, ion-dipole, or hydrogen-bonding interactions. Alkanes are non-polar because the C–H and C–C bonds distribute charge fairly evenly, giving no significant partial charges to interact with water. Water’s hydrogen-bonded network is already stable, so mixing with non-polar molecules doesn’t provide enough energy to break it and create favorable interactions. That’s why alkanes don’t dissolve in water. If a substance were polar, ionic, or hydrophilic, it would interact more strongly with water and dissolve.