Page 13 - 9-CHEM-6-newflip

6. Solution eLearn.Punjab

6.5. SOLUBILITY

Solubility is defined as the number of grams of the solute
dissolved in 100 g of a solvent to prepare a saturated
solution at a particular temperature. The concentration
of a saturated solution is referred to as solubility of the
solute in a given solvent.
Following are the factors which affect the solubility of solutes:
1. The general principle of solubility is, like dissolves like.
(i) The ionic and polar substances are soluble in polar solvents. Ionic solids and polar covalent

compounds are soluble in water e.g., KCl, Na2CO3, CuSO4, sugar, and alcohol are all soluble in
water.
(ii) Non-polar substances are not soluble in polar solvents. Non-polar covalent compounds are
not soluble in water such as ether, benzene, and petrol are insoluble in water.
(iii) Non-polar covalent substances are soluble in non-polar solvents (mostly organic solvents).
Grease, paints, naphthalene are soluble in ether or carbon tetrachloride etc.
2. Solute-solvent interaction.
3. Temperature.

6.5.1. Solubility and Solute-solvent interaction

The solute-solvent interaction can be explained in terms of creation of attractive forces between
the particles of solute and those of solvent. To dissolve one substance (solute) in another substance
(solvent) following three events must occur :
1. Solute particles must separate from each other.
2. Solvent particles must separate to provide space for solute particles.
3. Solute and solvent particles must attract and mix up.
Solution formation depends upon the relative strength of attractive forces between solute-solute,
solvent-solvent and solute-solvent. Generally solutes are solids.Ionic solids are arranged in such a
regular pattern that the inter-ionic forces are at a maximum. If the new forces between solute and
solvent particles overcome the solute-solute attractive forces, then solute dissolves and makes a
solution.

13