Question 1

Which of the following statements best describes the difference between a Bronsted-Lowry acid and a Lewis acid?

Accepted Answer

A Bronsted-Lowry acid donates a proton, while a Lewis acid accepts an electron pair.

Question 2

Given the following acid-base reaction:

$$\mathrm{CH_3COOH} + \mathrm{OH^-} \rightarrow \mathrm{CH_3COO^-} + \mathrm{H_2O}$$

Which species acts as the Bronsted-Lowry base?

Accepted Answer

$$\mathrm{OH^-}$$

Question 3

Which of the following equations correctly defines the acid dissociation constant $$K_a$$ for acetic acid ($$\mathrm{CH_3COOH}) in $$water?

Accepted Answer

$$K_a = \frac{[\mathrm{CH_3COO^-}][\mathrm{H_3O^+}]}{[\mathrm{CH_3COOH}]}$$

Question 4

Which of the following is the correct formula to calculate $$pK_a$$ from $$K_a$$?

Accepted Answer

$$pK_a = -\log_{10} K_a$$

Question 5

Consider the following acids and their $$pK_a$$ values:

$$\mathrm{HCl}$$ ($$pK_a = -7$$), $$\mathrm{CH_3COOH}$$ ($$pK_a = 4.8$$), $$\mathrm{H_2O}$$ ($$pK_a = 15.7$$), $$\mathrm{NH_3$}$$ ($$pK_a = 38)

$$Arrange these species in order of increasing acidity.

Accepted Answer

$$\mathrm{NH_3$} \u003c \mathrm{H_2O} \u003c \mathrm{CH_3COOH} \u003c \mathrm{HCl}$$

Question 6

Which of the following factors most increases the acidity of a hydrogen atom attached to a carbon atom?

Accepted Answer

The presence of electron-withdrawing groups near the carbon atom (inductive effect)

Question 7

Which of the following best explains why phenol ($$\mathrm{C_6H_5OH}) is $$more acidic than ethanol ($$\mathrm{CH_3CH_2OH}$$)?

Accepted Answer

The phenoxide ion is resonance stabilized, while the ethoxide ion is not.

Question 8

Given the following reaction and $$pK_a$$ values:

$$\mathrm{CH_3COOH} + \mathrm{F^-} \rightleftharpoons \mathrm{CH_3COO^-} + \mathrm{HF}$$

$$pK_a of$$ $$\mathrm{CH_3COOH} = 4.8$$, $$pK_a of$$ $$\mathrm{HF} = 3.2$$

Which direction does the equilibrium favor?

Accepted Answer

To the left (formation of $$\mathrm{CH_3COOH}$$ and $$\mathrm{F^-})$$

Question 9

Which of the following is a correct electron-pushing arrow for the deprotonation of ethanol ($$\mathrm{CH_3CH_2OH}) by $$sodium hydride ($$\mathrm{NaH}$$)?

Accepted Answer

An arrow from the lone pair on $$\mathrm{H^-} to $$the hydrogen of $$\mathrm{CH_3CH_2OH}$$, and an arrow from the O-H bond to the oxygen atom.

Question 10

Which of the following is the correct conjugate acid of ammonia ($$\mathrm{NH_3$}$$)?

Accepted Answer

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

Question 11

Which of the following functional groups contains a carbonyl group directly bonded to a nitrogen atom?

Accepted Answer

Amide

Question 12

Which of the following is a Lewis base?

Accepted Answer

$$\mathrm{NH_3$}$$

Question 13

Which of the following best describes the effect of resonance on the acidity of carboxylic acids?

Accepted Answer

Resonance stabilizes the conjugate base, increasing acidity.

Question 14

Which of the following correctly labels the acid and base in the reaction below?

$$\mathrm{H_2O} + \mathrm{NH_3$} \rightarrow \mathrm{OH^-} + \mathrm{NH_4$^+}$$

Accepted Answer

$$\mathrm{H_2O} = $$acid, $$\mathrm{NH_3$} = $$base

Question 15

Which of the following is the strongest acid?

Accepted Answer

$$\mathrm{HCl}$$

Question 16

Which of the following best explains why $$\mathrm{CF_3COOH} is a $$stronger acid than $$\mathrm{CH_3COOH}$$?

Accepted Answer

The $$\mathrm{CF_3$}$$ group is highly electronegative and stabilizes the conjugate base via inductive effects.

Question 17

Which of the following is the correct order of basicity for the following species?

$$\mathrm{NH_2$^-}$$, $$\mathrm{NH_3$}$$, $$\mathrm{NH_4$^+}$$

Accepted Answer

$$\mathrm{NH_2$^-} \u003e \mathrm{NH_3$} \u003e \mathrm{NH_4$^+}$$

Question 18

Which of the following is the correct electron-pushing arrow for the formation of the enolate ion from acetone ($$\mathrm{CH_3COCH_3}) $$using $$\mathrm{OH^-}$$?

Accepted Answer

An arrow from the lone pair on $$\mathrm{OH^-} to $$the alpha hydrogen, and an arrow from the C-H bond to the adjacent carbonyl carbon.

Question 19

Which of the following functional groups is present in both amino acids and proteins?

Accepted Answer

Amine and carboxylic acid

Thermodynamics, Acids, Bases, and Reaction Mechanisms (Chapter 4) Study Guide

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