Question

Understand what hydrogen bonding is and how that relates to water and the solubility of salts and other hydrophilic molecules

Answer 1

A hydrogen bond is the bonding between two polar groups that occurs when a hydrogen atom is bound to a highly electro negative atom. This is a n electrostatic attraction in which Hydrogen's electron will be use by the electronegative molecules like oxygen, fluorine or nitrogen. Hydrogen bonding can be within a molecule or in between molecules.

Water is made up of 2 Hydrogen atoms and one Oxygen atom. The Hydrogen atoms are slightly positively charged and the Oxygen atoms are slightly negatively charged. This feature allows water to participate in intermolecular hydrogen bonding with other water molecules.

The slight positive and negative charges (partial charges) in the water molecule result in net dipole moment, thus making water a polar molecule.

Salts readily dissociate into their respective ions in water as the positive ion is attracted by the slightly electronegative oxygen and negative ion is attracted by the slightly electropositive hydrogen. When a molecule of salt is dropped in water the molecules of water surround the salt molecule and lead to dissolution.

The case is similar with hydrophilic molecules also. Hydrophilic molecules are mostly polar substances that are readily attracted by water molecules.