The graph below is described verbally: a titration curve for the addition of a strong…
CHEMISTRY · Multi-part · A Level · Chemistry · Acids and bases · Acids and bases
Problem
The graph below is described verbally: a titration curve for the addition of a strong monoprotic acid to a weak base. The curve shows a pronounced buffer region, a gradual rise toward a midpoint, a steep drop near equivalence (pH ≈ 5.6), and then a long, nearly vertical tail that approaches pH ≈ 1.0 but never quite reaches it even with large excess volumes of acid.
Using this description, answer the following questions about the behavior of the solution in the post-equivalence region.
(a) Describe, in terms of relative concentrations of species present, why the pH in the tail region is controlled almost exclusively by the strong acid that has been added.
(b) Explain why the conjugate acid of the weak base does not significantly buffer the solution once the titration has passed the equivalence point.
(c) Theoretically, what pH value would the solution approach if an infinitely large volume of the titrant acid were added? Provide reasoning in support of your answer.
(d) Discuss how the slope of the titration curve in the tail region would change if the concentration of the strong acid titrant were doubled while all other conditions remained the same.