Aqueous Solution of NaCl(aq)Dissolving table salt, NaCl(s) into water, H2O.
You see that a crystal of NaCl(s) consists of cation, Na+ and anion, Cl-. During dissolving, one by one Na+ and Cl- are separated from the crystal, mix with water molecules.
Water molecule is a polar solvent and as a solute, salt is an ionic compound, so water has an ability to dissolve salt. This is because water and salt have a similar property, that is both have a charge. The charge of salt is come from the ions, cations and anions, and the charge of water is from its dipoles, positive poles and negative poles.
As you see from the picture, water molecules have a job to attract Na+ and Cl- from the salt. One by one, each ion is surrounded by water molecules, in another word, water molecules cover the salt ion. This process called SOLVATION. Na+ is surrounded by H2O with the negative poles (oxygen) are closely to the Na+. Cl- is surrounded by H2O with the positive poles are closely to the Cl-.
If there are a few of solute, so a lot of water molecules cover each ion of salt. The degree of dissociation of salt is 100%. Its mean, all salt can dissolve into water.
If there are a lot of solute, so water molecules are not enough to cover the salt ions. The salt ion cannot cover completely with water molecules. Because of this, Na+(aq) and Cl-(aq) can attract each other. This process called POLARIZATION. The degree of dissociation of salt is less than 100%.
Salt is a strong electrolyte, however, if the solution is too concentrated, there is a polarization.
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