question_answer 14)

Explain the following giving examples.                                               (a) saturated solution                  (b) pure substance                          (c) colloid                                      (d) suspension                                

Answer:

(a) Saturated solution : A solution in which no more solute can be dissolved in a given amount of solvent at a particular temperature is called saturated solution. For example, if we dissolve 40 g sodium chloride in 100 g of water at 293 K it will form a saturated solution because the solubility of sodium chloride at 293 K is 36 g per 100 g of water.    (b) Pure substance : A substance made up of only one kind of atoms or molecules is called a pure substance. A pure substance has the same colour taste and texture at a given temperature and pressure. A pure substance also has a fixed melting and boiling point at a constant pressure. For example hydrogen gas sodium chloride water etc.         (c) Colloid : A substance is said to be a colloid if its particles size lies between 1 to 100 nm. A colloidal solution is a heterogeneous and consists of two phases, i.e., dispersed phase (colloidal particles) and dispersion medium in which colloidal particles are suspended. For example colloidal solution of sulphur or starch milk etc.                          (d) Suspension : It is a heterogeneous mixture in which the particles of the solute do not dissolve but remain suspended throughout the bulk of the solvent. The size of the suspension particles is more than 10~7 m. For example, Chalk powder in water is a suspension.