# When an acid is added to a basic solution, what happens to the pH of the solution?

Consider the graph of $p H$ versus volume of solvent added in the appropriate acid base titration...........
Well before equivalence, addition of the acid titrant only marginally affects solution $p H$; we are still in the basic regime. Towards equivalence, the $p H$ changes dramatically, as the last excess of $H {O}^{-}$ is neutralized. Beyond equivalence, addition of further titrant only marginally decreases solution $p H$.