Question

Which of the following would help you identify a titration curve that involved a strong acid titrated by a weak base?

a.The pH at the equivalence point is lower than 7.
b.The pH at the equivalence point is higher than 7.
c.The titration curve begins at a higher pH and ends at a lower pH.
d.There is a rapid change in pH near the equivalence point (pH = 7).

Answer 1

The pH at the equivalence point is lower than 7

Step-by-step explanation:

Given the titration involves a strong acid and a weak base

An example is the reaction between ammonia and hydrochloric acid in the aqueous phase

The pH of the base will ordinarily start high and drop rapidly with the additions of acid. As the equivalence point is approached, the pH will change more gradually, until finally one drop will cause a rapid pH transition through the equivalence point.

If a chemical indicator is used—methyl orange would be a good choice in this case—it changes from its basic to its acidic colour.

In strong acid-weak base titrations, the pH at the equivalence point is not 7 but below it. This is due to the production of a conjugate acid during the titration; it will react with water to produce hydronium ions.