Question 1

Which of the following best explains why glycolic acid, a metabolite of ethylene glycol, is toxic to humans and animals?

Accepted Answer

It overwhelms the blood's buffer system, causing acidosis and reducing the ability of hemoglobin to carry oxygen.

Question 2

A buffer solution is prepared by mixing acetic acid ($$\mathrm{HC_2H_3O_2}) $$and sodium acetate ($$\mathrm{NaC_2H_3O_2}). $$Which equation correctly represents the equilibrium in this buffer?

Accepted Answer

$$\mathrm{HC_2H_3O_2} + \mathrm{H_2O} \rightleftharpoons \mathrm{C_2H_3O_2^-} + \mathrm{H_3O^+}$$

Question 3

Which of the following best describes the common ion effect?

Accepted Answer

Adding a salt containing the conjugate base of a weak acid suppresses the acid's ionization, raising the pH.

Question 4

Calculate the pH of a buffer solution that is $$0.14\ \mathrm{M} HF$$ ($$pK_a = 3.15) $$and $$0.071\ \mathrm{M} KF $$using the Henderson-Hasselbalch equation.

Accepted Answer

$$\mathrm{pH} = 3.15 + \log\left(\frac{0.071}{0.14}\right) = 2.86$$

Question 5

Which of the following statements about buffer capacity is correct?

Accepted Answer

Buffer capacity is greatest when the concentrations of acid and base are equal and large.

Question 6

A buffer is made by mixing $$0.100$$ mol $$\mathrm{HC_2H_3O_2}$$ and $$0.100$$ mol $$\mathrm{NaC_2H_3O_2} in$$ $$1.00 L. If$$ $$0.010$$ mol $$\mathrm{NaOH} is $$added, what are the new concentrations of $$\mathrm{HC_2H_3O_2}$$ and $$\mathrm{C_2H_3O_2^-}$$ after the reaction?

Accepted Answer

$$[\mathrm{HC_2H_3O_2}] = 0.090\ \mathrm{M},\ [\mathrm{C_2H_3O_2^-}] = 0.110\ \mathrm{M}$$

Question 7

Which acid would be the best choice to make a buffer with pH $$4.25$$?

Accepted Answer

Formic acid, $$pK_a = 3.74$$

Question 8

What is the relationship between $$pK_a$$ and $$pK_b$$ for a conjugate acid-base pair?

Accepted Answer

$$pK_a + pK_b = 14$$

Question 9

A $$25.0 mL $$sample of $$0.100 M $$HCl is titrated with $$0.100 M $$NaOH. What is the pH at the equivalence point?

Accepted Answer

$$\mathrm{pH} = 7.00$$

Question 10

Which of the following best describes the color change of an acid-base indicator?

Accepted Answer

It changes color over a pH range where $$[\mathrm{Ind^-}]$$ and $$[\mathrm{HInd}]$$ are both present in significant amounts.

Question 11

Which of the following statements about the solubility product ($$K_{sp}) is $$correct?

Accepted Answer

$$K_{sp} is $$the equilibrium constant for the dissolution of a solid salt into its ions.

Question 12

What will happen if the reaction quotient $$Q$$ for a salt in solution is greater than $$K_{sp}$$?

Accepted Answer

Precipitation will occur until $$Q = K_{sp}.$$

Question 13

Which of the following will increase the solubility of $$\mathrm{AgCl} in $$water?

Accepted Answer

Adding NH$$_3 to $$the solution, which forms a complex ion with Ag$$^+.$$

Question 14

A solution contains $$0.0175 M$$ $$\mathrm{Ca$$^{2+}$$}$$ and $$0.0175 M$$ $$\mathrm{OH^-}. If$$ $$K_{sp}$$ for $$\mathrm{Ca(OH)_2} is$$ $$4.68 	imes 10$$^{-6}$$, will a precipitate form?

Accepted Answer

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

Question 15

Which of the following best describes an amphoteric hydroxide?

Accepted Answer

A hydroxide that is more soluble in both acidic and basic solutions due to its ability to act as an acid or base.

Question 16

Which of the following is a correct application of the Henderson-Hasselbalch equation for a buffer made from a weak acid HA and its conjugate base A$$^-$$?

Accepted Answer

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

Question 17

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 18

Which of the following best explains why the pH at the equivalence point of a weak acid-strong base titration is greater than 7?

Accepted Answer

The conjugate base of the weak acid hydrolyzes to produce OH$$^-.$$

Aqueous Ionic Equilibrium: Buffers, Titrations, and Solubility

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