Question 1

Which of the following best describes the chemical process occurring at the equivalence point in a strong acid-strong base titration, as depicted in the first image?

Accepted Answer

All the H$$^+$$ ions have reacted with OH$$^-$$ ions to form water.

Question 2

In the titration setup shown in the second image, what is the primary function of the electrode immersed in the beaker?

Accepted Answer

To measure the pH of the solution during the titration.

Question 3

A student titrates 50.00 mL of 0.10 M HCl with 0.10 M NaOH. What is the pH after adding 25.00 mL of NaOH?

Accepted Answer

$$pH = -\log(0.033) = 1.48$$

Question 4

Which equation is used to calculate the pH of a buffer solution containing a weak acid and its conjugate base?

Accepted Answer

$$pH = pK_a + \log \frac{[A^-]}{[HA]}$$

Question 5

A buffer is prepared using 0.30 M acetic acid and 0.20 M sodium acetate. What is the pH of this buffer? ($$K_a = 1.8 	imes 10$$^{-5}$$)

Accepted Answer

$$pH = 4.744 + \log \frac{0.20}{0.30} = 4.57$$

Question 6

What is the buffer capacity most dependent on?

Accepted Answer

The total concentrations of the acid and its conjugate base.

Question 7

Which of the following statements about buffer solutions is FALSE?

Accepted Answer

A buffer is effective over any pH range.

Question 8

After adding 100.0 mL of 0.20 M NaOH to 1.00 L of a buffer containing 0.30 M acetic acid and 0.20 M sodium acetate, what is the new pH? ($$K_a = 1.8 	imes 10$$^{-5}$$)

Accepted Answer

$$pH = 4.64$$

Question 9

Which of the following best explains why the percent ionization of acetic acid is much lower in a buffer solution than in a solution containing only acetic acid?

Accepted Answer

The common ion effect suppresses ionization by shifting equilibrium to the left.

Question 10

What is the pH at the equivalence point when titrating 0.10 M HCl with 0.10 M NaOH?

Accepted Answer

$$pH = 7.00$$

Question 11

A buffer solution is most resistant to pH changes when:

Accepted Answer

$$pH = pK_a$$

Question 12

Which of the following is a correct statement about the endpoint in a titration?

Accepted Answer

It is detected by a sudden change in a physical property, usually color.

Question 13

If you want to prepare a buffer with pH 4.25 using acetic acid ($$pK_a = 4.74$$), what should the ratio $$\frac{[A^-]}{[HA]} be$$?

Accepted Answer

$$\frac{[A^-]}{[HA]} = 10$$^{-0.49}$$ = 0.32$$

Question 14

Which of the following best describes the useful pH range of a buffer?

Accepted Answer

$$pK_a \pm 1$$

Question 15

During a titration, why is it important to add the titrant slowly near the equivalence point?

Accepted Answer

The pH changes rapidly near the equivalence point, so slow addition allows for accurate determination.

Question 16

Which of the following is NOT a factor that affects buffer capacity?

Accepted Answer

The color of the indicator used.

Aqueous Ionic Equilibria: Buffers and Acid-Base Titrations

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