Question

(a) Differentiate between a saturated and an unsaturated solution. How will you test whether a given solution is saturated or not ?

(b) How would you prepare a saturated solution of sodium chloride in water at 25°C ? What will happen if this solution is cooled to 10°C ?

Answer 1

(a) A saturated solution is one that does not allow dissolution of additional solutes in it at a specific temperature.
An unsaturated solution is one that allows dissolution of additional solutes in it at the same temperature.

If a crystal dissolves in a solution, the solution is said to be unsaturated. This is because an unsaturated solution is capable of dissolving additional solutes into it.

A saturated solution does not dissolve additional solutes or crystals in it. Therefore, the crystal keeps its size when it is put in a saturated solution.

On cooling the solutions, the saturated solution will first form crystals.

(b) We will dissolve sodium chloride or NaCl in water in room temperature, till the water can no longer dissolve any more salt. By doing so, we will obtain a saturated solution of sodium chloride.
If the temperature is lowered from 25°C to 10°C, some of its dissolved solutes will get separated in the form of solute crystals due to the decrease in solubility of the solute.