Question 1

Which statement best describes a Bronsted-Lowry acid?

Accepted Answer

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

Question 2

In the reaction $$\mathrm{CH_3COOH} + \mathrm{H_2O} \rightleftharpoons \mathrm{CH_3COO^-} + \mathrm{H_3O^+}$$, which species is the conjugate base?

Accepted Answer

$$\mathrm{CH_3COO^-}$$

Question 3

Which curved arrow in a reaction mechanism represents the movement of electrons from a base to a proton?

Accepted Answer

An arrow starting at the lone pair of the base and pointing to the proton.

Question 4

Given the acid dissociation constant $$K_a = \dfrac{[\mathrm{H_3O^+}][\mathrm{A^-}]}{[\mathrm{HA}]}$$, what does a large $$K_a$$ value indicate?

Accepted Answer

The acid is strong.

Question 5

Which of the following statements about $$pK_a is $$correct?

Accepted Answer

A lower $$pK_a$$ value means a stronger acid.

Question 6

If the $$pK_a of $$acetic acid is 4.75 and the $$pK_a of $$water is 15.7, which direction will the equilibrium favor in the reaction $$\mathrm{CH_3COOH} + \mathrm{OH^-} \rightleftharpoons \mathrm{CH_3COO^-} + \mathrm{H_2O}$$?

Accepted Answer

Toward the products (right)

Question 7

Which factor is NOT part of the ARIO acronym for assessing conjugate base stability?

Accepted Answer

Solubility

Question 8

Why is acetic acid ($$\mathrm{CH_3COOH}) $$more acidic than ethanol ($$\mathrm{CH_3CH_2OH}$$)?

Accepted Answer

Because the conjugate base of acetic acid is resonance stabilized.

Question 9

Which of the following will increase the acidity of a carboxylic acid?

Accepted Answer

Adding electron-withdrawing groups near the carboxyl group.

Question 10

Which orbital holds a negative charge most stably?

Accepted Answer

$$sp$$

Question 11

Why is acetylene ($$\mathrm{HC\equiv CH}$$, $$pK_a = 25) $$more acidic than ethylene ($$\mathrm{H_2C=CH_2$}$$, $$pK_a = 44$$)?

Accepted Answer

Because the negative charge in acetylene's conjugate base is held in an $$sp$$ orbital.

Question 12

Which statement about the leveling effect of water is correct?

Accepted Answer

Water cannot be used as a solvent for acids stronger than $$\mathrm{H_3O^+} or $$bases stronger than $$\mathrm{OH^-}.$$

Question 13

Which of the following is a Lewis acid but NOT a Bronsted-Lowry acid?

Accepted Answer

$$\mathrm{BF_3$}$$

Question 14

Which of the following best explains why tert-butanol is less acidic than ethanol?

Accepted Answer

The tert-butoxide ion is less well solvated due to steric hindrance.

Question 15

In the reaction $$\mathrm{$$NaNH_2$$} + \mathrm{H_2O} \rightarrow \mathrm{NH_3$} + \mathrm{NaOH}$$, what role does $$\mathrm{Na^+}$$ play?

Accepted Answer

It is a counterion (spectator ion).

Question 16

Which of the following is the correct $$pK_a$$ relationship for predicting equilibrium position in an acid-base reaction?

Accepted Answer

Equilibrium favors the side with the weaker acid and weaker base.

Question 17

Which factor is most important when comparing the ability of oxygen and carbon to stabilize a negative charge in their conjugate bases?

Accepted Answer

Electronegativity for atoms in the same period.

Question 18

Which of the following statements about resonance stabilization is correct?

Accepted Answer

Resonance increases the acidity of a compound by stabilizing the conjugate base.

Question 19

Which of the following is true regarding the ARIO order of priority?

Accepted Answer

It is a helpful guideline but has exceptions.

Organic Chemistry Chapter 3: Acids and Bases – Study Notes

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