Q: Which of the following equations is the Henderson–Hasselbalch equation for an acidic buffer?

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

Question 1

Ethylene glycol, found in antifreeze, is metabolized in the liver to glycolic acid. Why is glycolic acid toxic to the body?

Accepted Answer

It overwhelms the blood's buffering ability, causing the blood pH to drop and leading to acidosis.

Question 2

Which of the following best describes a buffer solution?

Accepted Answer

A solution that contains significant amounts of a weak acid and its conjugate base.

Question 3

A buffer is prepared by mixing 0.100 M acetic acid ($$CH_3COOH) $$and 0.100 M sodium acetate ($$CH_3COONa). $$What happens to the pH if a small amount of HCl is added?

Accepted Answer

The pH decreases slightly because the acetate ion neutralizes the added acid.

Question 4

Which of the following equations is the Henderson–Hasselbalch equation for an acidic buffer?

Accepted Answer

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

Question 5

A buffer is made from a weak acid with $$pK_a = 4.82$$ and has a pH of 4.25. Which statement is true about the relative concentrations of the weak acid and its conjugate base?

Accepted Answer

The concentration of the weak acid is greater than that of the conjugate base.

Question 6

Which of the following actions would destroy a buffer made from 0.10 M HF and 0.050 M NaF in 1.0 L solution?

Accepted Answer

Adding 0.050 mole of HCl

Question 7

What is the pH at the half-equivalence point in the titration of a weak base with a strong acid if the $$pK_b of $$the weak base is 8.75?

Accepted Answer

8.75

Question 8

Which of the following best explains the common ion effect?

Accepted Answer

Adding a salt containing a common ion decreases the solubility of a weak acid by shifting the equilibrium to the left.

Question 9

A solution contains equal concentrations of $$Ag^+$$, $$Ba^{2+}$$, and $$Ca^{2+}. $$When potassium sulfate is added, which cation will precipitate first?

Accepted Answer

$$Ba^{2+}$$

Question 10

Which compound, when added to water, is most likely to increase the solubility of $$CuS$$?

Accepted Answer

$$NH_3$

Question 11

Which of the following statements about buffer capacity is correct?

Accepted Answer

Buffer capacity increases as the concentrations of the buffer components increase.

Question 12

A titration curve for a weak acid with a strong base shows a pH at the equivalence point that is:

Accepted Answer

Greater than 7

Question 13

Which of the following best describes the effect of pH on the solubility of an insoluble ionic hydroxide?

Accepted Answer

Lower pH increases solubility.

Question 14

Which of the following is true about the titration of a polyprotic acid?

Accepted Answer

There are two equivalence points if the acid has two ionizable protons.

Question 15

Which of the following is the correct expression for the solubility product constant ($$K_{sp}) $$for $$AgCl$$?

Accepted Answer

$$K_{sp} = [Ag^+][Cl^-]$$

Question 16

A buffer solution is most effective when:

Accepted Answer

The concentrations of acid and base are equal and large.

Question 17

Which of the following best describes selective precipitation?

Accepted Answer

A reagent is added to precipitate only one cation from a mixture based on differences in $$K_{sp}$$ values.

Question 18

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

Accepted Answer

It is the point where the indicator changes color, which should coincide with the equivalence point.

Question 19

Which of the following best explains why adding $$NH_3 to a $$solution containing $$AgCl$$ increases the solubility of $$AgCl$$?

Accepted Answer

$$NH_3$$ forms a complex ion with $$Ag^+$$, shifting the equilibrium to dissolve more $$AgCl.$$

Aqueous Ionic Equilibrium: Buffer Solutions, Titrations, and Solubility

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