


How do covalent bonds dissolve in water?

Covalent bonds do not dissolve in water, but some do.

When an ionic compound like NaCl dissolves in water, we end up with Na⁺ ions and Cl⁻ ions in solution.

This is a dissolving process, because the original compound contained the same ions.

When a covalent compound like HCl dissolves in water, we end up with H₃O⁺ ions and Cl⁻ ions in solution.

Although the covalent H-Cl bond breaks, this is a reaction process in which the products are soluble.

It is not a solution process, because the particles in solution are different from those in the original solute.

Covalent molecules attract each other by various intermolecular forces. These include H-bonds, dipole-dipole forces, and London dispersion forces.

Water molecules attract each other by strong H-bonds.

A polar may attract the water molecules as strongly as the water molecules attract each other.

It should contain a highly electronegative atom such as N or O or, even better, an N-H or an O-H bond, because they can form H-bonds to the water molecules.

It will then be able to work its way among the water molecules (dissolve).

Sugar and ethanol are covalent that are soluble in water, because they contain O-H groups that can H-bond to the water.

Nonpolar compounds like hydrocarbons have weak intermolecular attractive forces.

For example, hexane, C₆H₁₄, does not dissolve in water. Its molecules have little attraction to each other or to the water molecules.

The water molecules strongly attract each other. They stick together and keep out most of the hexane molecules.

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