SOLUBILITY
The solubility of a substance at given temperature is defined as the amount of solid that dissolves in 100g of the solvent to form a saturated solution.
SOLUBILITY OF SOLID IN LIQUID
1. The nature of solute and the solvent. This is in accordance with the basic rule ‘like dissolves like’.
This means ionic or polar compounds dissolve readily in polar solvents and are less or almost insoluble in non polar solvents
2. EFFECT OF TEMPERATURE
If the solute dissolves with absorption of heat (endothermic) the solubility increases with rise in temperature. If the solute dissolves with the evolution of heat (exothermic) the solubility decreases with increase in temperature.
3. EFFECT OF PRESSURE
On the solubility of solid in liquid is generally insignificant because solids and liquids are highly incompressible.
SOLUBILITY OF GAS IN LIQUID
1. Depends upon the nature of the gas and the nature of gas and nature of the liquid.
2. Generally the gases which can be easily liquefied are more soluble in common solvents.
3. The gases which are capable of forming ions in aqueous solution are much more soluble in water than in any other solvent.
4. EFFECT OF TEMPERATURE
The solubility of the gas in liquid decrease with rise in temperature.
5. EFFECT OF PRESSURE
The solubility of gas in liquid is governed by Henry’s law.
Higher the value of KH at a given pressure the lower is the solubility.
HENRY’S LAW
It states that the partial pressure in vapour phase (P) is proportional to the mole fraction of the gas(X) in the solution and is expressed as P= KHX , Where KH is the Henry’s Law constant.
Different gases have different KH values at same temperature.
It can also be defined as the mass of a gas dissolved per unit volume of the solvent at a given temperature is proportional to pressure of the gas in equilibrium with the solution.
APPLICATION OF HENRY’S LAW
REFER NCERT TEXT
SOLID SOLUTION
The solid solution are obtained by dissolving solid solute into solid solvent there are two types of solid solution.
SUBSTITUTIONAL SOLID SOLUTION
It is formed when particles of one substance in its crystal lattice.
Eg: brass, bronze etc
INTERSTITIAL SOLID SOLUTION
It is formed when atoms of one substance occupy the voids in the crystal lattice of host substance.
Eg: tungsten carbide
VAPOUR PRESSURE OF LIGUID SOLUTION
The pressure exerted by the vapour above the liquid surface in equilibrium with the liquid at a given temperature is called vapour pressure.
It can be explained in two ways
1. It states that at a given temperature, for a solution of volatile liquid the partial pressure of each component in the solution is directly proportional to the mole fraction of that compound.
2. It states that the vapour pressure of the solution is directly proportion to the mole fraction .
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