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

$$\mathrm{pH} = \mathrm{p}K_a + \log \left( \frac{[\text{base}]}{[\text{acid}]} \right)$$

Q: Which of the following is the correct formula for calculating the mass of sodium acetate needed to prepare a buffer?

$$\text{mass} = \text{moles} \times \text{molar mass}$$

Question 1

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

Accepted Answer

All the acid has been neutralized by the base, forming water and a salt.

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? Use $$\mathrm{pH} = -\log[\mathrm{H}_3\mathrm{O}^+].$$

Accepted Answer

$$\mathrm{pH} = 1.48$$

Question 4

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

Accepted Answer

$$\mathrm{pH} = \mathrm{p}K_a + \log \left( \frac{[	ext{base}]}{[	ext{acid}]} ight)$$

Question 5

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

Accepted Answer

$$\mathrm{pH} = 4.57$$

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 the endpoint and equivalence point in a titration is correct?

Accepted Answer

The endpoint is detected by a color change, while the equivalence point is the theoretical completion of the reaction.

Question 8

If 0.020 mol of NaOH is added 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

$$\mathrm{pH} = 4.64$$

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

A buffer is most effective when the ratio $$\frac{[	ext{base}]}{[	ext{acid}]} is$$:

Accepted Answer

1

Question 11

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

Accepted Answer

$$\mathrm{pH} = 7.00$$

Question 12

Which of the following is a correct statement about buffer range?

Accepted Answer

A buffer is effective within $$\mathrm{p}K_a \pm 1.$$

Question 13

After adding 55.00 mL of 0.10 M NaOH to 50.00 mL of 0.10 M HCl, what is the pH of the solution?

Accepted Answer

$$\mathrm{pH} = 11.68$$

Question 14

Which of the following best describes the purpose of a buffer solution in a biological or chemical system?

Accepted Answer

To resist changes in pH upon addition of small amounts of acid or base.

Question 15

Which of the following is the correct formula for calculating the mass of sodium acetate needed to prepare a buffer?

Accepted Answer

$$	ext{mass} = 	ext{moles} 	imes 	ext{molar mass}$$

Aqueous Ionic Equilibria: Buffers and Acid-Base Titrations

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