(a) Define a univ

(a) Universal indicator is a mixture of many different indicators which gives different colours at different pH values of the entire pH scale. It shows different colours at different concentrations of hydrogen ions in a solution.

(b) Solution A gives pink colour when a drop of phenolphthalein indicator is added, therefore A is a base.

Solution B gives red colour when a drop of methyl orange is added to it, therefore B is an acid Hence, solution A will have less concentration of hydrogen ion than B. Thus, A will have pH more than 7 because pH value of

— an acid solution < 7;

— a base solution > 7; and

— a neutral solution = 7.

(c) — The salts of strong acids and weak bases give acidic solution having pH less than 7. Example, NH₄Cl, Ammonium Chloride will have pH less than 7.

— The salts of weak acids and strong give basic solution having pH more than 7. Example, Na₂CO₃, Sodium Carbonate will have pH more than 7.