Mass of potassium chloride in 100 g of water in saturated solution = 37 g
Mass of potassium chloride in 60 g of water in saturated solution = \(\frac{37}{100}\)× 60
= 22.2 g

(i) The number of water molecule in blue vitriol is five.
(ii) The hot saturated solution of copper sulphate has no water molecule.
(iii) When cooled the hot saturated solutions gain five molecules of water and it will turn to crystal.

(i) A solution must at least be consisting of two components ( a solute and a solvent ).
(ii) Such solution which are made of one solute and one solvent (two components) are called binary solution.
(iii) e.g: On addition copper sulphate crystals to water.

(i) A solution is a homogeneous mixture of two or more substances.
E g: Sea water.
(ii) In a solution, the component present in lesser amount by weight is called a solute.
(iii) The component present in a larger amount by weight is called a solvent.
(iv) Solute + Solvent → Solution

There are three main factors which govern the solubility of a solute. They are:
a) Nature of the solute and solvent
b) Temperature
c) Pressure
a) Nature of the solute and solvent:
(i) The nature of the solute and solvent plays an important role in solubility.
(ii) Although water dissolves an enormous variety of substances, both ionic and covalent, it does not dissolve everything.
(iii) The phrase that scientists often use when predicting solubility is "like dissolves like".
(iv) The expression means that dissolving occurs when similarities exist between the solvent and the solute.
(v) For example: Common salt is a polar compound 4 and dissolves readily in polar solvent like water.
(vi) Non-polar compounds are soluble in non-polar solvents. For example: Fat dissolved in ether.
(vii) But non-polar compounds, do not dissolve in polar solvents; polar compounds do not dissolve in non-polar solvents.
b) Effect of Temperature:
Solubility of Solids in Liquid:
(i) Generally, solubility of a solid solute in a liquid solvent increases with increase in temperature.
(ii) For example, a greater amount of sugar will dissolve in warm water than in cold water.
(iii) In endothermic process, solubility increases with increase in temperature.
(iv) In exothermic process, solubility decreases with increase in temperature.
Solubility of Gases in liquid:
(i) Solubility of gases in liquid decrease with increase in temperature.
(ii) Generally, water contains dissolved oxygen.
(iii) When water is boiled, the solubility of oxygen in water decreases, so oxygen escapes in the form of bubbles.
(iv) Aquatic animals live more in cold regions because, more amount of dissolved oxygen is present in the water of cold regions.
(v) This shows that the solubility of oxygen in water is more at low temperatures.
c) Effect of Pressure:
(i) Effect of pressure is observed only in the case of solubility of a gas in a liquid.
(ii) When the pressure is increased, the solubility of a gas in liquid increases.
(iii) The common examples for solubility of gases in liquids are carbonated beverages, i.e. soft drinks, household cleaners containing aqueous solution of ammonia, formalin aqueous solution of formaldehyde, etc.

(i) Saturated solution:
a) A solution in which no more solute can be dissolved in a definite amount of the solvent at a given temperature is called saturated solution.
b) E.g. 36 g of sodium chloride in 100 g of water at 25° C forms saturated solution.
c) Further addition of sodium chloride, leaves it undissolved.
(ii) Unsaturated solution:
a) Unsaturated solution is one that contains less solute than that of the saturated solution at a given temperature.
b) E.g. 10 g or 20 g or 30 g of Sodium chloride in 100 g of water at 25°C forms an unsaturated solution.