SOLUTIONS

9.4 - Solubility of Ionic Compounds

In section 5.1, we learned that compounds which have ionic bonds are called ionic compounds. In section 5.1.3, we learned that in aqueous solution, an ionic compound dissociates into its ions and giving the solution the ability to conduct electricity. Any substance that gives ions in an aqueous solution and thereby conducts electricity is called an electrolyte.

As an ionic solid such as NaCl dissolves in water, water molecules must overcome the forces which hold ions together to make them go into solution. The polar water molecules are attracted to both positive and negative ions of the ionic solid.

	View an animation on Strong Electrolyte, Weak Electrolyte, Non-electrolyte (Flash plugin required)

Look carefully at the above diagram and see that the positive ions are attracted by the oxygen atom of the water and the negative ions are attracted by the more positive hydrogen atoms of water. Once an ion is surrounded by the water molecules, an ion is freed from the lattice and a hydrated ion is formed.

The process of going into solution may be exothermic or endothermic.

Section 14.2
Types of Solutions ..p363

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