Question

Equal volumes of two monoprotic acid solutions (A and B) are titrated with identical NaOH solutions. The volume to reach the equivalence point for solution A is twice the volume required to reach the equivalence point for solution B, and the pH at the equivalence point of solution A is higher than the pH at the equivalence point for solution B. Which statement is true?
A) The acid in solution A is less concentrated than in solution B and is also a weaker acid than that in solution B.
B) The acid in solution A is more concentrated than in solution B and is also a stronger acid than that in solution B.
C) The acid in solution A is less concentrated than in solution B and is also a stronger acid than that in solution B.
D) The acid in solution A is more concentrated than in solution B and is also a weaker acid than that in solution B.

Answer 1

Answer:

D

Explanation:

It looks like two things are being looked at here; the concentration and strength of acid. Titrations show volume and are not affected by the strength of the acid, so let's start with that. Since twice the volume of NaOH is needed to reach equivalence point, there must be a higher concentration of A, as the chemical equation must be the same (it says that they're both monoprotic acids, so the chemical equation doesn't change). This eliminates A and C.

As for pH; if it is higher at equivalence point, it wasn't as strong at moving the pH down despite being in NaOH(a strong base); and since solution A has a higher pH at equivalence point, it isn't as strong as solution B.

This eliminates B.

The answer is D.

This seems like a normal AP Chemistry question, but then again titrations are important to know in chemistry.

Answer 2

Answer:

D. Solution A has more concentrated acid than solution B and acid in solution A is also a weaker acid than that in solution B.

Explanation:

As it has been said in the question that the volume to reach the equivalence point of the solution A is twice the volume of solution B, this is because the acid in the solution A is more concentrated than B that's why more NaOH was required to reach to the equivalence point.

Since the pH at the equivalence point was greater for solution A that means the acid in solution A was a weak acid that's why the pH raised more as the NaOH was added to the solution.