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

$$\mathrm{pH} = \mathrm{p}K_a + \log \frac{[\text{conjugate base}]}{[\text{weak acid}]}$$

Question 1

A dog is seen drinking a green liquid leaking from a car, which is likely ethylene glycol (antifreeze). Ethylene glycol poisoning can cause metabolic acidosis. Which buffer system in the human body is primarily responsible for resisting changes in blood pH in this scenario?

Accepted Answer

The bicarbonate buffer system

Question 2

Which of the following best describes how a buffer solution resists changes in pH when a small amount of strong acid is added?

Accepted Answer

The strong acid reacts with the conjugate base in the buffer, forming more weak acid.

Question 3

Given a buffer solution made by mixing 0.10 M acetic acid ($$\mathrm{HC_2H_3O_2}) $$and 0.10 M sodium acetate ($$\mathrm{NaC_2H_3O_2}$$), what is the pH of the solution? ($$K_a$$ for acetic acid = $$1.8 	imes 10$$^{-5}$$)

Accepted Answer

$$\mathrm{pH} = 4.7$$

Question 4

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

Accepted Answer

$$\mathrm{pH} = \mathrm{p}K_a + \log \frac{[	ext{conjugate base}]}{[	ext{weak acid}]}$$

Question 5

A buffer is most effective when:

Accepted Answer

The concentrations of weak acid and conjugate base are equal

Question 6

Which of the following mixtures will NOT result in a buffer solution?

Accepted Answer

0.10 M hydrochloric acid and 0.10 M sodium chloride

Question 7

A buffer is prepared by mixing 0.14 M HF ($$pK_a = 3.74) $$and 0.071 M KF. What is the pH of the buffer?

Accepted Answer

$$\mathrm{pH} = 3.43$$

Question 8

Which acid would be best to prepare a buffer with a pH of 7.38?

Accepted Answer

Hypochlorous acid ($$pK_a = 7.54)$$

Question 9

During the titration of a weak acid with a strong base, what is true at the half-equivalence point?

Accepted Answer

The pH equals the pKa of the weak acid

Question 10

Which of the following statements about the titration curve of a strong acid with a strong base is correct?

Accepted Answer

The equivalence point occurs at pH = 7

Question 11

Which of the following best explains why the solubility of AgCl decreases when NaCl is added to the solution?

Accepted Answer

The common ion effect shifts the equilibrium to the left

Question 12

Calculate the molar solubility of AgCl in pure water if $$K_{sp} = 1.8 	imes 10$$^{-10}$$.

Accepted Answer

$$1.3 	imes 10$$^{-5}$$ M$

Question 13

Which of the following will increase the solubility of Mg(OH)$$_2 in $$water?

Accepted Answer

Decreasing the pH by adding HCl

Question 14

A solution contains 0.0052 M Ca$$^{2+}$$ and 0.0041 M SO$$_4$$^{2-}$$. If these concentrations are doubled by evaporation, will CaSO_4$ precipitate? (K$$_{sp}$$ for CaSO_4$ = 2.4$$ 	imes $$10^{-5})$$

Accepted Answer

Yes, because $$Q \u003e K_{sp}$$

Question 15

Which of the following best describes an amphoteric hydroxide?

Accepted Answer

A hydroxide that reacts with both acids and bases

Question 16

Which of the following cations will NOT precipitate as a chloride upon addition of HCl in qualitative analysis?

Accepted Answer

Na$$^+$$

Question 17

Which of the following best explains why AgCl dissolves in aqueous ammonia?

Accepted Answer

Ammonia forms a complex ion with Ag$$^+$$, increasing its solubility

Question 18

Which of the following is the correct net ionic equation for the neutralization of acetic acid by sodium hydroxide?

Accepted Answer

$$\mathrm{CH_3COOH} + \mathrm{OH^-} \rightarrow \mathrm{CH_3COO^-} + \mathrm{H_2O}$$

Aqueous Ionic Equilibrium: Buffers, Titrations, and Solubility

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