Q: A solution is prepared by dissolving 0.10 M acetic acid ($$\mathrm{HC_2H_3O_2}) in $$water. The $$K_a$$ for acetic acid is $$1.8 \times 10$$^{-5}$$. Using the approximation method, what is the equilibrium concentration of $$\mathrm{H_3O^+}$$, and is the approximation valid?

$$[\mathrm{H_3O^+}] = 1.3 \times 10$$^{-3}$$\ \mathrm{M}$$; valid because x/0.10 = 1.3\% \u003c 5\%

Q: A solution of $$\mathrm{HCOOH} ($$formic acid) has a pH of 2.38. What is the $$[\mathrm{H_3O^+}] in $$this solution?

$$4.2 \times 10$$^{-3}$$\ \mathrm{M}$$

Q: Which of the following is the correct formula for calculating percent ionization of a weak acid?

$$\frac{[\mathrm{H_3O^+}]_{eq}}{[\mathrm{HA}]_{initial}} \times 100$$

Q: Which of the following statements is true regarding the autoionization of water at $$25^\circ\mathrm{C}$$?

$$[\mathrm{H_3O^+}] = [\mathrm{OH^-}] = 1.0 \times 10$$^{-7}$$\ \mathrm{M}$$

Question 1

Which of the following statements best describes the Brønsted-Lowry definition of an acid?

Accepted Answer

An acid is a proton donor.

Question 2

A solution is prepared by dissolving 0.10 M acetic acid ($$\mathrm{HC_2H_3O_2}) in $$water. The $$K_a$$ for acetic acid is $$1.8 	imes 10$$^{-5}$$. Using the approximation method, what is the equilibrium concentration of $$\mathrm{H_3O^+}$$, and is the approximation valid?

Accepted Answer

$$[\mathrm{H_3O^+}] = 1.3 	imes 10$$^{-3}$$\ \mathrm{M}$$; valid because x/0.10 = 1.3\% \u003c 5\%

Question 3

Which of the following is an example of an amphiprotic species?

Accepted Answer

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

Question 4

Given the reaction $$\mathrm{$$HNO_2$$(aq) + H_2O(l) \rightleftharpoons NO_2$^-(aq) + H_3O^+(aq)}$$, identify the conjugate acid-base pairs.

Accepted Answer

Acid: $$\mathrm{$$HNO_2$$}$$, Base: $$\mathrm{H_2O}$$, Conjugate Acid: $$\mathrm{H_3O^+}$$, Conjugate Base: $$\mathrm{NO_2$^-}$$

Question 5

Which of the following acids is the strongest according to the acid strength table?

Accepted Answer

$$\mathrm{H_3O^+}$$

Question 6

A solution has $$[\mathrm{OH^-}] = 2.0 	imes 10$$^{-5}$$\ \mathrm{M} at$$ $$25^\circ\mathrm{C}. $$What is the pH of the solution?

Accepted Answer

$$pH = 9.30 ($$since $$pOH = 4.70$$, $$pH = 14.00 - 4.70 = 9.30)$$

Question 7

Which of the following best describes the relationship between $$K_a$$ and $$K_b$$ for a conjugate acid-base pair?

Accepted Answer

$$K_a 	imes K_b = K_w$$

Question 8

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

Accepted Answer

$$\mathrm{NaCH_3COO}$$

Question 9

A 0.15 M solution of ammonia ($$\mathrm{NH_3$}) $$has a $$K_b of$$ $$1.8 	imes 10$$^{-5}$$. What is the pH of the solution?

Accepted Answer

$$pH = 11.20$$

Question 10

Which of the following factors increases the acidity of an oxyacid $$\mathrm{HOY}$$?

Accepted Answer

Increasing the number of oxygen atoms bonded to Y

Question 11

Which of the following is a Lewis acid?

Accepted Answer

$$\mathrm{BF_3$}$$

Question 12

A solution of $$\mathrm{HCOOH} ($$formic acid) has a pH of 2.38. What is the $$[\mathrm{H_3O^+}] in $$this solution?

Accepted Answer

$$4.2 	imes 10$$^{-3}$$\ \mathrm{M}$$

Question 13

Which of the following best explains why $$\mathrm{Cl^-}$$ does not affect the pH of a solution?

Accepted Answer

$$\mathrm{Cl^-} is $$the conjugate base of a strong acid.

Question 14

Which of the following solutions will have the lowest pH?

Accepted Answer

0.10 M $$\mathrm{HCl}$$

Question 15

Which of the following is the correct formula for calculating percent ionization of a weak acid?

Accepted Answer

$$\frac{[\mathrm{H_3O^+}]_{eq}}{[\mathrm{HA}]_{initial}} 	imes 100$$

Question 16

Which of the following best describes the effect of a small, highly charged metal cation (e.g., $$\mathrm{Al$$^{3+}$$}) on $$the pH of water?

Accepted Answer

It decreases the pH by making water more acidic.

Question 17

Which of the following statements is true regarding the autoionization of water at $$25^\circ\mathrm{C}$$?

Accepted Answer

$$[\mathrm{H_3O^+}] = [\mathrm{OH^-}] = 1.0 	imes 10$$^{-7}$$\ \mathrm{M}$$

Question 18

Which of the following acids has the largest $$K_a$$ value?

Accepted Answer

$$\mathrm{CF_3CO_2H}$$

Question 19

A solution is prepared by dissolving $$\mathrm{NaClO} in $$water, resulting in a pH of 10.50. Which ion is responsible for the basicity, and what reaction occurs?

Accepted Answer

$$\mathrm{ClO^-}$$; $$\mathrm{ClO^-} + H_2O \rightarrow HClO + OH^-$$

Acids and Bases: Concepts, Calculations, and Applications

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