Question 1

Which of the following best describes a buffer solution?

Accepted Answer

A solution that resists changes in pH when small amounts of acid or base are added.

Question 2

Which combination will form a buffer solution?

Accepted Answer

0.1 M CH₃COOH and 0.1 M CH₃COONa

Question 3

Which of the following is NOT a property of a buffer solution?

Accepted Answer

It contains a strong acid and a strong base.

Question 4

The buffer system in human blood is primarily composed of which pair?

Accepted Answer

$$\mathrm{H_2CO_3}$$ / $$\mathrm{$$HCO_3$$^-}$$

Question 5

What happens when a small amount of strong acid is added to a buffer solution containing a weak acid and its conjugate base?

Accepted Answer

The conjugate base neutralizes the added acid, minimizing the pH change.

Question 6

Calculate the pH of a buffer solution containing 0.1 M acetic acid ($$\mathrm{CH_3COOH}$$, $$K_a = 1.8 	imes 10$$^{-5}$$) and 0.1 M sodium acetate ($$\mathrm{CH_3COONa}$$).

Accepted Answer

$$4.74$$

Question 7

Which equation is used to calculate the pH of a buffer solution?

Accepted Answer

$$\mathrm{pH = pK_a + \log \left( \frac{[A^-]}{[HA]} \right)}$$

Question 8

A buffer solution is made by mixing 0.05 M $$\mathrm{HC_2H_3O_2}$$ and 0.15 M $$\mathrm{NaC_2H_3O_2}. If$$ $$K_a = 6.5 	imes 10$$^{-5}$$, what is the pH?

Accepted Answer

$$4.71$$

Question 9

Which of the following will NOT form a buffer solution?

Accepted Answer

0.1 M $$\mathrm{$$HNO_3$$}$$ and 0.1 M $$\mathrm{$$NaNO_3$$}$$

Question 10

If 25.0 mL of 1.0 M NaOH is added to 100 mL of a buffer containing 0.1 M HA and 0.1 M A$$^-$$ ($$K_a = 1.8 	imes 10$$^{-5}$$), what is the new pH? (Assume total volume is additive.)

Accepted Answer

$$5.11$$

Question 11

Which of the following statements is TRUE regarding the effect of adding a strong base to a buffer solution?

Accepted Answer

The weak acid in the buffer neutralizes the added base.

Question 12

Given $$K_a = 7.1 	imes 10$$^{-4}$$ for HF, what is the pH of a buffer solution containing 0.5 M HF and 0.75 M KF?

Accepted Answer

$$3.32$$

Question 13

Which of the following best explains why strong acids and strong bases do NOT form buffer solutions?

Accepted Answer

They completely dissociate in water and do not provide a conjugate pair to resist pH changes.

Question 14

What is the correct relationship between $$K_a$$ and acid strength?

Accepted Answer

The larger the $$K_a$$, the stronger the acid.

Question 15

A buffer solution contains 0.1 M HA and 0.1 M A$$^-. If$$ $$K_a = 1.8 	imes 10$$^{-5}$$, what is the percent ionization of HA?

Accepted Answer

$$0.84\%$$

Question 16

Which of the following is the correct Henderson-Hasselbalch equation?

Accepted Answer

$$\mathrm{pH = pK_a + \log \left( \frac{[A^-]}{[HA]} \right)}$$

Question 17

If the $$x-$$small approximation is NOT valid for a buffer solution, what method should be used to calculate the pH?

Accepted Answer

Use the ICE table and solve the quadratic equation.

Question 18

A buffer solution is prepared by mixing 0.1 M pyridine (a weak base) and 0.1 M pyridinium chloride (its conjugate acid). What will happen to the pH if a small amount of HCl is added?

Accepted Answer

The pH will decrease slightly, but the buffer will resist a large change.

Question 19

Which of the following best describes the role of the conjugate base in a buffer solution when acid is added?

Accepted Answer

It neutralizes the added acid.

Aqueous Ionic Equilibrium: Buffer Solutions and pH Calculations

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