Q: Which of the following pairs could be used to make a buffer solution with a pH close to 4.7?

$$\mathrm{CH_3COOH}$$ \ \text{and} \ \mathrm{CH_3COONa}$

Q: A $$0.010\ \mathrm{M}$$ solution of a weak acid has a pH of $$3.00. $$What is the $$[\mathrm{OH^-}] in $$the solution?

$$1.0 \times 10$$^{-11}$$\ \mathrm{M}$$

Question 1

Which of the following best describes a Bronsted-Lowry acid?

Accepted Answer

A substance that donates a proton ($$\mathrm{H^+}) to $$another substance.

Question 2

Which of the following substances can act as both a Bronsted-Lowry acid and a Bronsted-Lowry base (i.e., is amphoteric)?

Accepted Answer

$$\mathrm{H_2O}$$

Question 3

Given the reaction: $$\mathrm{NH_3$ + H_2O \rightarrow NH_4$^+ + OH^-}$$, which of the following is the conjugate acid of $$\mathrm{NH_3$}$$?

Accepted Answer

$$\mathrm{NH_4$^+}$$

Question 4

Which of the following is a Lewis acid but NOT an Arrhenius acid?

Accepted Answer

$$\mathrm{BF_3$}$$

Question 5

Which of the following equations represents the first dissociation step of the polyprotic acid $$\mathrm{H_2SO_4} in $$water?

Accepted Answer

$$\mathrm{H_2SO_4 + H_2O \rightarrow $$HSO_4$$^- + H_3O^+}$$

Question 6

Which of the following statements best explains why $$\mathrm{Ka_1$ \u003e Ka_2$ \u003e Ka_3$}$$ for a polyprotic acid?

Accepted Answer

Each successive proton is removed from a more negatively charged species, making it harder to remove.

Question 7

Which of the following acids is expected to be the strongest based on molecular structure?

Accepted Answer

$$\mathrm{$$HClO_4$$}$$

Question 8

A solution has $$[\mathrm{H_3O^+}] = 1.0 	imes 10$$^{-5}$$\ \mathrm{M}. $$What is the pH of the solution?

Accepted Answer

$$5.0$$

Question 9

If $$[\mathrm{OH^-}] = 2.0 	imes 10$$^{-3}$$\ \mathrm{M} at$$ $$25^\circ\mathrm{C}$$, what is the pH of the solution? ($$K_w = 1.0 	imes 10$$^{-14}$$)

Accepted Answer

$$2.7$$

Question 10

Which of the following salts will produce a basic solution when dissolved in water?

Accepted Answer

$$\mathrm{NaF}$$

Question 11

Which of the following pairs could be used to make a buffer solution with a pH close to 4.7?

Accepted Answer

$$\mathrm{CH_3COOH}$$ \ 	ext{and} \ \mathrm{CH_3COONa}$

Question 12

A buffer is prepared by mixing $$0.20\ \mathrm{mol} of$$ $$\mathrm{NH_3$}$$ and $$0.20\ \mathrm{mol} of$$ $$\mathrm{NH_4Cl} in$$ $$1.0\ \mathrm{L} of $$solution. If $$K_b$$ for $$\mathrm{NH_3$} is$$ $$1.8 	imes 10$$^{-5}$$, what is the pH of the buffer? (pK_b = 4.74$)

Accepted Answer

$$9.26$$

Question 13

Which of the following best describes the common ion effect?

Accepted Answer

The addition of an ion common to an equilibrium shifts the equilibrium to reduce the concentration of that ion.

Question 14

During the titration of $$25.0\ \mathrm{mL} of$$ $$0.100\ \mathrm{M}$$ acetic acid ($$K_a = 1.8 	imes 10$$^{-5}$$) with 0.100$$\ \mathrm{M}$$ NaOH, what is the pH at the half-equivalence point?

Accepted Answer

$$4.74$$

Question 15

Which indicator would be most appropriate for the titration of a strong acid with a strong base?

Accepted Answer

Bromothymol blue (pH transition range: 6.0–7.6)

Question 16

Which of the following best explains why 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 $$\mathrm{OH^-}.$$

Question 17

Which of the following equations correctly relates $$K_a$$ and $$K_b$$ for a conjugate acid-base pair?

Accepted Answer

$$K_a 	imes K_b = K_w$$

Question 18

A $$0.010\ \mathrm{M}$$ solution of a weak acid has a pH of $$3.00. $$What is the $$[\mathrm{OH^-}] in $$the solution?

Accepted Answer

$$1.0 	imes 10$$^{-11}$$\ \mathrm{M}$$

Question 19

Which of the following best defines buffer capacity?

Accepted Answer

The amount of acid or base a buffer can neutralize before a significant change in pH occurs.

Acids, Bases, and Aqueous Equilibria: Definitions, Calculations, and Applications

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