Solubility


Solubility of a substance is its maximum amount that can be dissolved in a specified amount of solvent at a specified temperature. There are many factors that contribute to solubility, like solvent, solute, temperature, etc.

Various types of Solutions and there solubility:

1. Solubility of a Solid in a Liquid
Every solid does not dissolve in a given liquid. There is a certain properties of solids due to which they don't dissolve in liquids. eg naphthalene doesn't dissolve in water while NaCl does. 
Polar solutes dissolve in polar solvents and non polar solutes in non-polar solvents. A solute dissolves in a solvent if the inter-molecular interactions are similar to each other.

There are two separate processes taking place while mixing a solid in a liquid
a. Dissolution: It is the process when solid particles are dissolving in the solution and increasing its concentration
b. Crystallization: When solid solute particles collide with each other in solution and get separated out.

Both the above processes are happening simultaneously. But there appears a stage when an equilibrium is achieved, This a stage when number of particles dissolving is equal to particles crystallizing

Once an equilibrium is achieved, the concentration of solutions becomes constant( if temperature, pressure , etc other parameters are not changed). 

A solution in which no more solute can be dissolved in the solvent is called as Saturated solution. And a solution in which there can be more addition of solute in solvent is called as Unsaturated Solution.


Effects of Environmental conditions affects the solutbility of substance in solution:
1. Temperature Variation
Temperature directly affects the solubility of solute in an solvent, nearly saturated solution, the dissolution process is endothermic (Dsol H > 0), the solubility should increase with rise in temperature and if it is exothermic (Dsol H < 0) the solubility should decrease.

2. Pressure Variation
Change in pressure virtually has no effect on solubility of solids in liquids


2. Solubility of a Gas in a Liquid

There are many gases which are soluble in liquid solvents. However the solubility varies from gas to gas. eg O2 is soluble in very limited quantities, while gases like HCl are highly soluble.
Unlike the solid Solutes, solubility of gaseous solutes depend heavily on environmental factors.

1. Effects of pressure variation
The solubility of gases increase with increase of pressure.

2. Effects of temperature variation
Solubility of gases in liquids decreases with rise in temperature.


Related Tutorials