Five solutions A, B, C, D and E when tested with universal indicator showed pH as 4, 1, 11, 7 and 9 respectively.

(a) Which solution is (i) neutral (ii) strongly alkaline (iii) strongly acidic (iv) weakly acidic, and (v) weakly alkaline?

(b) Arrange the pH values in the increasing order of hydrogen ion concentration.

(a) (i) The pH of neutral solution is 7. Thus, the neutral solution is D with pH=7.

(ii) The pH value of greater than 7 indicates the basic solution. Higher pH value represents strong alkaline solution. Thus, strong alkaline solution is C with pH=11.

(iii) The pH value of less than 7 indicates the acidic solution. Lower pH value represents strong acidic solution. Thus, strong acidic solution is B with pH=1.

(iv) weakly acidic: A (pH=4);

(v) weakly alkaline: E (pH=9)

(b) pH scale quantifies the concentration of hydrogen ion in a solution. The pH value increases with decrease in hydrogen ion concentration. The solution having pH 11 will have the minimum hydrogen ion concentration than the solution having pH 1. Thus, arrangement of solutions in the increasing order of their hydrogen ion concentrations as follows:

C < E <D <A <B
(pH 11) < (pH 9) <(pH 7)< (pH 4)< (pH 1)