(i) The purpose of the pH scale is to determine the nature (acidic, basic or neutral) of a given solution.
(ii) The pH value of pure water is 7. Pure water is neutral in nature.
(iii) On the pH scale, bases (or alkalis) have a pH value greater than 7, while acids have a pH value below 7. The pH value of neutral solutions is 7.
(a) A solution of A will have a pH value less than 7 as compared to pH of water.
(b) A solution of B will have a pH value greater than 7 as compared to pH of water.