(a) Define a universel indicator. Mention its one use.
(b) Solution A gives pink colour when a deop of phenolphthalein indicator is added to it. Solution B gives a red colour when a drop of methyl orange is added to it. What type or solution are A and B and which of these will have higher pH value ?
(c) Name one salt whose solution has pH less then 7 and one salt with pH more than 7.

Explanation

(a) A universal indicatro is a mixture of several indicators. By comparason, it can predict the pH value of a solution. For details, consult section 2.6.
(b) Solution A is acidic whereas solution B is of basic nature. Solution B has a higher pH value.
(c ) A salt of strong acid and weak base (e.g., `NH_(4)Cl)` has pH less than 7. A salt of weak acid and strong base `(e.g.,Na_(2)CO_(3))` has pH more than 7.