Q: A solution has [H$$_3O$^+$$] = $$1.0 \times 10$$^{-5}$$ M at 25$$^\circ$$C. What is the pH of the solution?

$$\mathrm{pH} = -\log_{10}(1.0 \times 10$$^{-5}$$) = 5.0$$

Q: Calculate the pOH of a solution with [OH$$^-$$] = $$2.5 \times 10$$^{-3}$$ M.

$$\mathrm{pOH} = -\log_{10}(2.5 \times 10$$^{-3}$$) = 2.60$$

Q: A solution has a pH of 3.0. What is the concentration of H$$_3O$^+ in $$the solution?

$$[\mathrm{H_3O}^+] = 1.0 \times 10$$^{-3}$$ M

Q: If the $$K_a of an $$acid is $$1.0 \times 10$$^{-6}$$, what is its pK_a$?

$$pK_a = -\log_{10}(1.0 \times 10$$^{-6}$$) = 6.0$$

Question 1

Which of the following best describes a Brønsted–Lowry acid?

Accepted Answer

A substance that donates a proton

Question 2

Which of the following is the conjugate base of H$$_2PO$_4^-$$?

Accepted Answer

HPO$$_4$$^{2-}$$

Question 3

A solution has [H$$_3O$^+$$] = $$1.0 	imes 10$$^{-5}$$ M at 25$$^\circ$$C. What is the pH of the solution?

Accepted Answer

$$\mathrm{pH} = -\log_{10}(1.0 	imes 10$$^{-5}$$) = 5.0$$

Question 4

Which of the following statements about the autoprotolysis of water is correct?

Accepted Answer

It produces equal concentrations of H$$_3O$^+$$ and OH$$^-$$ ions.

Question 5

Which of the following acids is stronger: acetic acid ($$K_a = 1.8 	imes 10$$^{-5}$$) or formic acid (K_a = 1.8$$ 	imes $$10^{-4}$$)?

Accepted Answer

Formic acid, because it has a higher $$K_a$$ value.

Question 6

A buffer solution is prepared by mixing equal concentrations of acetic acid and sodium acetate. What will happen to the pH if a small amount of HCl is added?

Accepted Answer

The pH will decrease slightly.

Question 7

Which of the following equations represents the ionization of a weak acid HA in water?

Accepted Answer

$$\mathrm{HA}(aq) + \mathrm{H_2O}(l) \rightleftharpoons \mathrm{H_3O}^+(aq) + \mathrm{A}^-(aq)$$

Question 8

Calculate the pOH of a solution with [OH$$^-$$] = $$2.5 	imes 10$$^{-3}$$ M.

Accepted Answer

$$\mathrm{pOH} = -\log_{10}(2.5 	imes 10$$^{-3}$$) = 2.60$$

Question 9

Which of the following best explains why HCl is a strong acid?

Accepted Answer

It completely dissociates in aqueous solution.

Question 10

A solution has a pH of 3.0. What is the concentration of H$$_3O$^+ in $$the solution?

Accepted Answer

$$[\mathrm{H_3O}^+] = 1.0 	imes 10$$^{-3}$$ M

Question 11

Which of the following is a correct expression for the acid dissociation constant $$K_a$$ for the weak acid HA?

Accepted Answer

$$K_a = \dfrac{[\mathrm{H_3O}^+][\mathrm{A}^-]}{[\mathrm{HA}]}$$

Question 12

Which of the following pairs is a conjugate acid–base pair?

Accepted Answer

NH$$_4^+$$ and NH$$_3$$

Question 13

If the $$K_a of an $$acid is $$1.0 	imes 10$$^{-6}$$, what is its pK_a$?

Accepted Answer

$$pK_a = -\log_{10}(1.0 	imes 10$$^{-6}$$) = 6.0$$

Question 14

Which of the following best describes the effect of adding NaOH to a buffer solution containing CH$$_3$$COOH and CH$$_3$$COO$$^-$$?

Accepted Answer

The pH will increase slightly.

Question 15

Which of the following is the correct Henderson–Hasselbalch equation for a buffer solution?

Accepted Answer

$$\mathrm{pH} = pK_a + \log_{10}\left(\dfrac{[\mathrm{A}^-]}{[\mathrm{HA}] }\right)$$

Question 16

Which of the following factors increases the strength of a binary acid HX?

Accepted Answer

Decreasing bond strength between H and X

Question 17

A lake has a [H$$_3O$^+$$] of $$2.5 	imes 10$$^{-6}$$ M. What is the pH of the lake?

Accepted Answer

$$\mathrm{pH} = -\log_{10}(2.5 	imes 10$$^{-6}$$) = 5.60$$

Question 18

Which of the following is a property of a strong base in aqueous solution?

Accepted Answer

It completely dissociates to produce OH$$^-$$ ions.

Question 19

Which of the following best explains why buffer solutions are important in biological systems?

Accepted Answer

They maintain a relatively constant pH.

Acids, Bases, and Aqueous Equilibria: Brønsted–Lowry Theory, pH, and Buffer Solutions

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