Question 1

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

Accepted Answer

A substance that donates a proton ($$H^+).$$

Question 2

In the reaction $$CH_3COOH + H_2O \rightarrow CH_3COO^- + H_3O^+$$, which species is the conjugate base?

Accepted Answer

$$CH_3COO^-$$

Question 3

Which factor is most important when comparing the ability of atoms in the same period to stabilize a negative charge?

Accepted Answer

Electronegativity

Question 4

Given the following acids and their $$pK_a$$ values: HBr ($$pK_a = -9$$), HCl ($$pK_a = -7$$), and HF ($$pK_a = 3$$), which is the strongest acid?

Accepted Answer

HBr

Question 5

Which of the following best explains why acetic acid ($$CH_3COOH) is $$more acidic than ethanol ($$CH_3CH_2OH$$)?

Accepted Answer

The conjugate base of acetic acid is resonance stabilized.

Question 6

Which of the following statements about the leveling effect is correct?

Accepted Answer

Water can act as both an acid and a base, limiting the strength of acids and bases that can be used.

Question 7

Which of the following is NOT a factor in the ARIO acronym for assessing conjugate base stability?

Accepted Answer

Solubility

Question 8

Predict the direction of equilibrium for the following reaction, given the $$pK_a$$ values: $$NH_3$$ ($$pK_a = 38) $$and $$CH_3CH_2OH$$ ($$pK_a = 16$$): $$NH_3 + CH_3CH_2OH$$ \rightleftharpoons $$NH_2^- + CH_3CH_2OH_2$$^+$$.

Accepted Answer

Equilibrium favors the reactants.

Question 9

Which of the following best describes a Lewis acid?

Accepted Answer

A substance that accepts a pair of electrons.

Question 10

Why is acetylene ($$C_2H_2) $$more acidic than ethylene ($$C_2H_4) $$and ethane ($$C_2H_6$$)?

Accepted Answer

The negative charge in acetylene's conjugate base resides in an orbital with more s-character.

Question 11

Which of the following is true regarding the effect of electron-withdrawing groups on acidity?

Accepted Answer

Electron-withdrawing groups stabilize the conjugate base by inductively withdrawing electron density.

Question 12

A student mixes sodium amide ($$NaNH_2) $$with water. What will happen?

Accepted Answer

Sodium amide will deprotonate water, forming $$NH_3$$ and $$OH^-.$$

Question 13

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

Accepted Answer

The conjugate base of $$t-$$butanol is less stabilized by solvation due to steric hindrance.

Question 14

Which of the following is the correct curved arrow notation for the acid-base reaction between $$CH_3COOH$$ and $$OH^-$$?

Accepted Answer

Arrow from $$OH^-$$ lone pair to the acidic hydrogen of $$CH_3COOH$$, and arrow from O-H bond to $$CH_3COO$$ oxygen.

Question 15

Which of the following is true about the zwitterionic form of an amino acid at physiological pH?

Accepted Answer

The amino group is protonated and the carboxylic acid group is deprotonated.

Question 16

Which of the following is a correct statement about the relationship between acid strength and conjugate base strength?

Accepted Answer

A strong acid has a weak conjugate base.

Question 17

Which of the following is the best method to predict the position of equilibrium in an acid-base reaction if $$pK_a$$ values are unknown?

Accepted Answer

Compare the stability of the conjugate bases.

Question 18

Which of the following reactions can be classified as a Lewis acid-base reaction but NOT a Brønsted-Lowry acid-base reaction?

Accepted Answer

Formation of $$BF_3-$$ether complex.

Question 19

Which of the following statements about counterions is correct?

Accepted Answer

Counterions are necessary to balance the overall charge but are often omitted from reaction equations.

Organic Chemistry Chapter 3: Acids and Bases (Study Notes)

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