Question 1

Which of the following statements correctly describes the relationship between Brønsted and Lewis acids?

Accepted Answer

All Brønsted acids are Lewis acids.

Question 2

Given the following reaction: $$\mathrm{$$AlCl_3$$} + \mathrm{CH_3OCH_3} \rightarrow \mathrm{AlCl_3OCH_3}$$, which species acts as the Lewis base?

Accepted Answer

$$\mathrm{CH_3OCH_3}$$

Question 3

Which of the following compounds has the lowest $$pK_a$$ value and is therefore the strongest acid?

Accepted Answer

Formic acid ($$pK_a = 3.75)$$

Question 4

Which of the following best explains why $$\mathrm{HF} is a $$weaker acid than $$\mathrm{HI}$$?

Accepted Answer

Hydrogen is more tightly bound to fluorine due to its smaller atomic size.

Question 5

What is the $$pK_a$$ range for a moderately strong acid?

Accepted Answer

$$pK_a = 1-3$$

Question 6

In the reaction $$\mathrm{CH_3OH} + \mathrm{H_2O} \rightarrow \mathrm{CH_3O^-} + \mathrm{H_3O^+}$$, which species is the conjugate base?

Accepted Answer

$$\mathrm{CH_3O^-}$$

Question 7

Which factor most strongly influences acid strength when comparing $$\mathrm{CH_4$}$$, $$\mathrm{NH_3$}$$, $$\mathrm{H_2O}$$, and $$\mathrm{HF}$$?

Accepted Answer

Electronegativity of the atom bonded to hydrogen

Question 8

Which of the following is true regarding the relationship between $$K_a$$ and $$pK_a$$?

Accepted Answer

As $$K_a$$ increases, $$pK_a$$ decreases.

Question 9

Which of the following alcohols is the weakest acid?

Accepted Answer

Ethyl alcohol ($$pK_a = 15.9)$$

Question 10

A curved arrow in a reaction mechanism always points:

Accepted Answer

From the electron donor to the electron acceptor

Question 11

Which of the following is a correct expression for the acid dissociation constant $$K_a$$ for the reaction $$\mathrm{HA} + \mathrm{H_2O} \rightleftharpoons \mathrm{H_3O^+} + \mathrm{A^-}$$?

Accepted Answer

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

Question 12

Which of the following is the strongest base?

Accepted Answer

Methylamine ($$pK_a = 40)$$

Question 13

Which of the following statements about Lewis bases is correct?

Accepted Answer

Lewis bases donate a share in an electron pair.

Question 14

Which of the following is a correct definition of a Brønsted acid?

Accepted Answer

A species that donates a proton.

Question 15

Which of the following factors increases the stability of a conjugate base, thereby increasing acid strength?

Accepted Answer

Delocalization of the negative charge by resonance

Question 16

Which of the following is true about the acid-base reaction between acetic acid ($$pK_a = 4.76) $$and methylamine ($$pK_a = 40$$)?

Accepted Answer

The equilibrium favors the formation of acetate and methylammonium.

Question 17

Which of the following is the correct $$pK_a$$ value for ammonia?

Accepted Answer

$$pK_a = 36$$

Question 18

Which of the following statements best describes the effect of inductive electron withdrawal on acid strength?

Accepted Answer

It stabilizes the conjugate base, making the acid stronger.

Question 19

Which of the following is the strongest acid based on hybridization effects?

Accepted Answer

Ethyne ($$\mathrm{HC\equiv CH})$$

Question 20

Which of the following is the correct formula for calculating $$pK_a$$?

Accepted Answer

$$pK_a = -\log K_a$$

Acids and Bases in Organic Chemistry

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