When a monoprotic weak acid is titrated with a strong base, the titration curve contains these many inflection points:
a.zero
b.one
c.two
d.three
Can you also explain why you choose your answer to this question...thanks
To determine the number of inflection points in the titration curve of a monoprotic weak acid titrated with a strong base, we need to understand the concept of inflection points and the behavior of weak acids during titration.
Inflection points occur when the rate of change of pH with respect to the volume of added titrant changes. These points are significant because they indicate changes in the chemical species being present in the solution.
A monoprotic weak acid is an acid that can donate only one proton (H+) during a reaction. When this type of acid is titrated with a strong base, the following stages occur:
1. Initial stage: Before any base is added, the solution contains only the weak acid (HA) and its conjugate base (A-). The pH is determined by the dissociation of HA into H+ and A-. At this stage, the pH is determined by the equilibrium of the acid and its conjugate base.
2. Buffer stage: As the strong base is added, it combines with the weak acid to form the conjugate base of the acid and water. The solution acts as a buffer, maintaining a relatively stable pH as long as a significant amount of weak acid and its conjugate base exist in the solution. During this stage, the pH remains relatively constant. The buffer region in the titration curve represents this stage.
3. Equivalence point: The equivalence point is the point at which the amount of strong base added is stoichiometrically equal to the amount of weak acid present. At this point, all of the weak acid is neutralized, and the solution contains only the conjugate base of the weak acid. The pH at the equivalence point is determined by the hydrolysis of the conjugate base.
Based on this analysis, we can conclude that a monoprotic weak acid titrated with a strong base will have a titration curve with two inflection points:
1. The first inflection point occurs during the buffer stage, representing the transition from the initial pH determined by the equilibrium of the weak acid and its conjugate base to a relatively constant pH as the buffering capacity of the solution is exhausted.
2. The second inflection point occurs at the equivalence point, representing the transition from the acidic buffer to a more alkaline solution as the weak acid is completely neutralized, and the solution consists mainly of the conjugate base.
Therefore, the correct answer to the question is c. two inflection points.