Question 1

Which of the following best describes a substitution reaction in organic chemistry?

Accepted Answer

A reaction in which one group replaces another within a molecule.

Question 2

Which of the following statements about Brønsted–Lowry acids and bases is correct?

Accepted Answer

A Brønsted–Lowry acid is a substance that donates a proton, while a Brønsted–Lowry base accepts a proton.

Question 3

Which of the following is the strongest acid that can exist in water to any significant extent?

Accepted Answer

$$\mathrm{H_3O^+}$$

Question 4

Which of the following best describes a Lewis acid?

Accepted Answer

A substance that accepts an electron pair.

Question 5

Carbocations are considered:

Accepted Answer

Electrophiles because they are electron-deficient and seek electrons.

Question 6

Which of the following statements about nucleophiles is correct?

Accepted Answer

Nucleophiles are Lewis bases that seek a positive center.

Question 7

Which of the following correctly represents the relationship between acid strength and pKa?

Accepted Answer

The smaller the pKa, the stronger the acid.

Question 8

Given the following acids and their pKa values, which is the strongest acid?

$$\mathrm{CH_3CO_2H}$$: $$pK_a = 4.75$$

$$\mathrm{CF_3CO_2H}$$: $$pK_a = 0$$

$$\mathrm{HCl}$$: $$pK_a = -7$$

Accepted Answer

$$\mathrm{HCl}$$

Question 9

Which of the following statements about conjugate acids and bases is correct?

Accepted Answer

The stronger the acid, the weaker its conjugate base.

Question 10

Predict the direction of the following acid–base reaction at equilibrium:

$$\mathrm{CH_3CO_2H} + \mathrm{HO^-} \rightleftharpoons \mathrm{CH_3CO_2^-} + \mathrm{H_2O}$$

Given $$pK_a(\mathrm{CH_3CO_2H}) = 4.75$$ and $$pK_a(\mathrm{H_2O}) = 15.7.$$

Accepted Answer

The reaction favors the formation of $$\mathrm{CH_3CO_2^-}$$ and $$\mathrm{H_2O}.$$

Question 11

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

Accepted Answer

Increasing the s character of the carbon atom's hybrid orbital.

Question 12

Which of the following best explains why acetic acid ($$\mathrm{CH_3CO_2H}) is a $$stronger acid than ethanol ($$\mathrm{CH_3CH_2OH}$$)?

Accepted Answer

The conjugate base of acetic acid is stabilized by resonance delocalization.

Question 13

Which of the following statements about inductive effects is correct?

Accepted Answer

Inductive effects weaken as the distance from the group increases.

Question 14

A carboxylic acid with a chlorine atom attached to the alpha carbon is more acidic than acetic acid because:

Accepted Answer

Chlorine stabilizes the conjugate base via its electron-withdrawing inductive effect.

Question 15

Which of the following equations correctly relates the standard free energy change ($$\Delta G^\circ) to $$the equilibrium constant ($$K_{eq}$$)?

Accepted Answer

$$\Delta G^\circ = -RT \ln K_{eq}$$

Question 16

Which of the following best explains why most carboxylic acids with more than five carbons are insoluble in water, but become soluble in aqueous NaOH?

Accepted Answer

The acid reacts with NaOH to form a polar carboxylate salt, which is water-soluble.

Question 17

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

Accepted Answer

Solvation stabilizes ions, making it easier to separate them and increasing acid strength in solution.

Question 18

Which of the following is a correct statement about the use of curved arrows in reaction mechanisms?

Accepted Answer

Curved arrows show the direction of electron flow, from the source of an electron pair to the atom receiving the pair.

Question 19

Which of the following best describes the relationship between potential energy and stability in molecules?

Accepted Answer

The more potential energy a molecule has, the less stable it is.

Question 20

Amines with high molecular weights are generally insoluble in water, but become soluble in aqueous acid because:

Accepted Answer

Amines react with acid to form water-soluble ammonium salts.

Organic Reactions and Their Mechanisms: Acids and Bases

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