Question 1

Which of the following statements best describes the difference between the Arrhenius and Brønsted-Lowry definitions of acids and bases?

Accepted Answer

Arrhenius acids increase the concentration of H+ in aqueous solution, while Brønsted-Lowry acids donate H+ ions to any base.

Question 2

Given the reaction: $$\mathrm{HCl} + \mathrm{H_2O} \rightarrow \mathrm{H_3O^+} + \mathrm{Cl^-}$$, which species acts as the Brønsted-Lowry base?

Accepted Answer

$$\mathrm{H_2O}$$

Question 3

Which of the following compounds is the strongest acid based on their pKa values?

Accepted Answer

Hydrochloric acid ($$\mathrm{HCl}$$), $$pK_a = -7.0$$

Question 4

Which of the following best explains why fluoroacetic acid ($$pK_a = 2.59) is a $$stronger acid than chloroacetic acid ($$pK_a = 2.86$$)?

Accepted Answer

Fluorine is more electronegative than chlorine, stabilizing the negative charge on the conjugate base.

Question 5

Which of the following statements about resonance and acid strength is correct?

Accepted Answer

Resonance in the conjugate base increases acid strength by stabilizing the negative charge.

Question 6

Which of the following is the conjugate base of $$\mathrm{$$HSO_4$$^-}$$?

Accepted Answer

$$\mathrm{SO_4$^{2-}}$$

Question 7

A solution contains acetic acid ($$pK_a = 4.76). If $$the pH of the solution is 3.0, which form of acetic acid will predominate?

Accepted Answer

The acidic form (protonated acetic acid)

Question 8

Which of the following best describes why the acetate ion is more stable than the ethoxide ion?

Accepted Answer

The acetate ion has resonance stabilization, delocalizing the negative charge.

Question 9

Which of the following statements about the effect of hybridization on acidity is correct?

Accepted Answer

An increase in s character increases acid strength.

Question 10

Which of the following compounds is expected to be the strongest acid?

Accepted Answer

Ethyne ($$pK_a = 25)$$

Question 11

Which of the following best explains why 2-chlorobutanoic acid ($$pK_a = 2.86) is a $$stronger acid than 4-chlorobutanoic acid ($$pK_a = 4.52$$)?

Accepted Answer

The chlorine atom is closer to the carboxyl group in 2-chlorobutanoic acid, increasing inductive electron withdrawal.

Question 12

Which of the following is a Lewis acid in the reaction: $$\mathrm{$$AlCl_3$$} + \mathrm{CH_3OCH_3} \rightarrow \mathrm{Cl_3AlOCH_3}$$?

Accepted Answer

$$\mathrm{$$AlCl_3$$}$$

Question 13

Which of the following best describes the effect of increasing atomic size on acid strength for hydrogen halides?

Accepted Answer

Acid strength increases as atomic size increases.

Question 14

Which of the following is the conjugate acid of $$\mathrm{$$HCO_3$$^-}$$?

Accepted Answer

$$\mathrm{H_2CO_3}$$

Question 15

A mixture of anisole and benzoic acid is dissolved in $$\mathrm{D_2O}$$ and extracted with $$\mathrm{NaOH} (aq). $$Which compound will be found in the aqueous layer after extraction?

Accepted Answer

Benzoic acid, because it forms a water-soluble carboxylate ion.

Question 16

Which of the following statements about the Henderson-Hasselbalch equation is correct?

Accepted Answer

When $$\mathrm{pH} = \mathrm{p}K_a$$, the concentrations of acid and conjugate base are equal.

Question 17

Which of the following is the strongest conjugate base?

Accepted Answer

Ethoxide ion ($$\mathrm{CH_3CH_2O^-})$$

Question 18

Which of the following best explains why alcohols are weaker acids than carboxylic acids?

Accepted Answer

Carboxylic acids have inductive electron withdrawal and resonance stabilization.

Question 19

Which of the following is the correct arrow-pushing mechanism for the reaction of water with a proton ($$\mathrm{H^+}$$)?

Accepted Answer

The arrow starts at the lone pair on oxygen and points to the hydrogen atom.

Acids and Bases: Definitions, Strength, and Structure in Organic Chemistry

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