Question 1

The titration curve shown represents the titration of a 0.100 M solution of an unknown acid with 0.100 M NaOH. Based on the two distinct buffer regions and two equivalence points, what type of acid is being titrated?

Accepted Answer

A diprotic acid

Question 2

At approximately what pH does the first equivalence point occur in the titration curve, and what does this indicate about the acid being titrated?

Accepted Answer

Around pH 4.5, indicating a weak acid

Question 3

If the volume at the first equivalence point is approximately 15 mL, what is the total number of moles of acid originally present in the solution? Use the formula $$n = M_1V_1 = M_2V_2$$ where $$M_2 = 0.100$ M and V_2$ = 0.015 L.$$

Accepted Answer

$$1.50 	imes 10$$^{-3}$$ mol

Question 4

Which of the following best explains why there are two distinct buffer regions in the titration curve?

Accepted Answer

The acid has two ionizable protons with significantly different $$pK_a$$ values.

Question 5

If the first buffer region occurs at a pH of approximately 3.5, what is the $$pK_a of $$the first ionization of the acid?

Accepted Answer

$$pK_a \approx 3.5$$

Question 6

What is the best explanation for the steep rise in pH at each equivalence point in the titration curve?

Accepted Answer

All of the acid has been neutralized, so the solution rapidly becomes basic.

Question 7

If a student titrates a diprotic acid with NaOH and observes only one equivalence point, what is the most likely explanation?

Accepted Answer

The two $$pK_a$$ values are too close together to be distinguished.

Question 8

Suppose the second equivalence point occurs at 30 mL of NaOH added. What is the molar ratio of NaOH to acid at this point?

Accepted Answer

2:1

Question 9

Which of the following real-world substances could produce a titration curve similar to the one shown?

Accepted Answer

Oxalic acid ($$H_2C_2O_4)$$

Question 10

If the initial pH of the solution is approximately 2, what does this suggest about the acid being titrated?

Accepted Answer

It is a moderately strong diprotic acid.

Analyzing a Titration Curve: Diprotic Acid with Strong Base

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