Question 1

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

Accepted Answer

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

Question 2

What is the pH of a $$0.001 M $$solution of $$\mathrm{HCl} (a $$strong acid) at $$25^\circC$$?

Accepted Answer

$$3$$

Question 3

Which of the following statements is TRUE regarding the relationship between $$K_a$$ and acid strength?

Accepted Answer

A larger $$K_a$$ value indicates a stronger acid.

Question 4

A buffer solution is prepared by mixing $$0.20$$ mol of acetic acid ($$\mathrm{CH_3COOH}) $$and $$0.20$$ mol of sodium acetate ($$\mathrm{CH_3COONa}) in$$ $$1.0 L of $$water. If the $$K_a of $$acetic acid is $$1.8 	imes 10$$^{-5}$$, what is the pH of the buffer? ($$\log 1.8 \approx 0.26$$)

Accepted Answer

$$4.74$$

Question 5

Which of the following best explains why the pH of a buffer solution changes only slightly when a small amount of strong acid is added?

Accepted Answer

The weak base component of the buffer neutralizes the added acid.

Question 6

Which of the following is the correct expression for the $$K_b of $$ammonia ($$\mathrm{NH_3$}) in $$water?

Accepted Answer

$$K_b = \frac{[\mathrm{NH_4$^+}][\mathrm{OH^-}]}{[\mathrm{NH_3$}]}$$

Question 7

A $$0.10 M $$solution of a weak acid has a pH of $$3.0. $$What is the $$[\mathrm{H^+}] in $$this solution?

Accepted Answer

$$1.0 	imes 10$$^{-3}$$ M

Question 8

Which of the following pairs would NOT form a buffer solution when mixed in equal concentrations?

Accepted Answer

$$\mathrm{HCl}$$ and $$\mathrm{NaCl}$$

Question 9

If the $$K_a of a $$weak acid is $$1.0 	imes 10$$^{-5}$$, what is the pK_a$?

Accepted Answer

$$5.0$$

Question 10

A $$0.10 M $$solution of a weak base has a pOH of $$3.0. $$What is the $$[\mathrm{OH^-}] in $$this solution?

Accepted Answer

$$1.0 	imes 10$$^{-3}$$ M

Question 11

During the titration of a weak acid with a strong base, which of the following best describes the pH at the equivalence point?

Accepted Answer

The pH is greater than $$7$$ because the conjugate base of the weak acid hydrolyzes to produce $$\mathrm{OH^-}.$$

Question 12

Which of the following is the correct relationship between $$K_a$$, $$K_b$$, and $$K_w$$ for a conjugate acid-base pair?

Accepted Answer

$$K_a 	imes K_b = K_w$$

Question 13

A $$0.10 M $$solution of a weak acid is $$2\%$$ ionized. What is the $$[\mathrm{H^+}] in $$the solution?

Accepted Answer

$$2.0 	imes 10$$^{-3}$$ M

Question 14

Which of the following best explains why a strong acid has a lower pH than a weak acid of the same concentration?

Accepted Answer

A strong acid ionizes completely, producing a higher $$[\mathrm{H^+}].$$

Question 15

Which of the following is the correct order of acid strength (from strongest to weakest) for the following acids: $$\mathrm{HCl}$$, $$\mathrm{CH_3COOH}$$, $$\mathrm{H_2CO_3}$$?

Accepted Answer

$$\mathrm{HCl} \u003e \mathrm{CH_3COOH} \u003e \mathrm{H_2CO_3}$$

Question 16

A buffer is made by mixing $$0.50$$ mol of $$\mathrm{NH_3$}$$ and $$0.25$$ mol of $$\mathrm{NH_4Cl} in$$ $$1.0 L of $$solution. If $$K_b$$ for $$\mathrm{NH_3$} is$$ $$1.8 	imes 10$$^{-5}$$, what is the pH of the buffer? (K_w = 1.0$$ 	imes $$10^{-14}$$, $$\log 1.8 \approx 0.26)$$

Accepted Answer

$$9.43$$

Question 17

Which of the following best describes the effect of dilution on the pH of a buffer solution?

Accepted Answer

The pH remains nearly constant because the ratio of acid to base does not change.

Question 18

During the titration of a strong acid with a strong base, what is the pH at the equivalence point?

Accepted Answer

$$7$$

Question 19

Which of the following is the correct formula for calculating the pH of a solution given $$[\mathrm{H^+}]$$?

Accepted Answer

$$\mathrm{pH} = -\log [\mathrm{H^+}]$$

Question 20

A solution has a pOH of $$5.0. $$What is the pH of the solution at $$25^\circC$$?

Accepted Answer

$$9.0$$

Acid-Base Equilibria and Additional Aspects of Aqueous Equilibria: Study Notes

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