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IB DP Chemistry Questions

18.3 pH Curves

Question 1

During a titration between a strong acid and a strong base, at what point is the pH equal to 7?

A. At the start of the titration

B. Halfway to the equivalence point

C. At the equivalence point

D. At the end of the titration

Question 2

Which of the following combinations will result in a buffer solution during a titration?

A. Strong acid and its conjugate base

B. Weak acid and strong base

C. Strong acid and strong base

D. Weak acid and its conjugate base

Question 3

In a titration between a weak acid and a strong base, where is the pH greater than 7?

A. At the start of the titration

B. Halfway to the equivalence point

C. At the equivalence point

D. At the end of the titration

Question 4

Which of the following is NOT a characteristic of the buffer region in a pH curve?

A. It has a relatively flat portion of the curve

B. The pH changes slowly with the addition of titrant

C. It is where the equivalence point occurs

D. It can resist changes in pH

Question 5

What is the pH at the equivalence point when titrating a weak base with a strong acid?

A. Less than 7

B. Equal to 7

C. Greater than 7

D. Cannot be determined

Question 6

a) Explain the significance of the equivalence point on a pH curve during a titration. [2]

b) During the titration of a weak acid with a strong base, why does the pH at the equivalence point exceed 7? [2]

Question 7

a) Describe the buffer region observed on a pH curve. [2]

b) Why is the pH change minimal in the buffer region even when a significant amount of titrant is added? [2]

Question 8

a) How can the strength of an unknown acid be determined using a pH curve? [2]

b) Why is the initial pH lower in the titration of a strong acid with a strong base compared to the titration of a weak acid with a strong base? [2]

Question 9

a) Define the terms Ka and Kb in the context of acid-base equilibria. [2]

b) How are Ka and Kb related to the ion product constant for water, Kw? [2]

c) If the Ka for an acid HA is 2.5 x 10^-5, calculate the Kb for its conjugate base A-. [3]

Question 10

a) What is the significance of the half-equivalence point in a pH curve? [2]

b) How can one determine the pKa of a weak acid using its titration curve? [3]

c) Explain why the pH at the half-equivalence point is independent of the concentration of the weak acid. [2]

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