Question 1

Which of the following best describes the role of the curved arrows in the acid-base mechanism shown below?

$$\ce{B:^- + H-A  B-H + :A^-}

($$Arrows show electron movement from B: to H, and from H-A bond to A)

Accepted Answer

They show the movement of electron pairs from the base to the proton and from the bond to the leaving group.

Question 2

Dextromethorphan is often administered as its HBr salt. What is the role of HBr in this reaction?

$$\ce{Dextromethorphan + HBr -\u003e Dextromethorphan-H^+ + Br^-}$$

Accepted Answer

HBr acts as a Brønsted-Lowry acid, donating a proton to dextromethorphan.

Question 3

Which of the following antacid ingredients acts as a Brønsted-Lowry base in the stomach?

A) Sodium bicarbonate
B) Calcium carbonate
C) Bismuth subsalicylate
D) Benzocaine

Accepted Answer

Sodium bicarbonate

Question 4

Given the following equilibrium:

$$\ce{HA + H2O  A^- + H3O^+}

If$$ $$K_{eq} \u003e 1$$, which of the following statements is true?

Accepted Answer

The products (A$$^-$$ and H3O$$^+) $$are favored at equilibrium.

Question 5

Which of the following acids is the strongest based on the pKa values below?

A) Alcohol, $$pK_a = 16
B) $$Carboxylic acid, $$pK_a = 5
C) $$Phenol, $$pK_a = 10
D) $$Alkyne, $$pK_a = 25$$

Accepted Answer

Carboxylic acid

Question 6

Which of the following statements about the relationship between $$pK_a$$ and acid strength is correct?

Accepted Answer

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

Question 7

Which of the following best explains why 2-chlorobutanoic acid ($$pK_a = 2.83) is a $$stronger acid than butanoic acid ($$pK_a = 4.82$$)?

Accepted Answer

The chlorine atom increases inductive electron withdrawal, stabilizing the conjugate base.

Question 8

Which of the following bases is the strongest according to the ARIO (or CARIO) principles?

A) $$\ce{CH3O^-}
B$$) $$\ce{CH3S^-}
C$$) $$\ce{CH3NH^-}
D$$) $$\ce{CH3COO^-}$$

Accepted Answer

$$\ce{CH3O^-}$$

Question 9

Which of the following statements about orbital hybridization and acidity is correct?

Accepted Answer

An sp-hybridized atom is more acidic than an sp$$^3-$$hybridized atom.

Question 10

Which of the following best describes the effect of resonance on conjugate base stability?

Accepted Answer

Resonance delocalization increases conjugate base stability.

Question 11

Which of the following solvents would be most appropriate for using a strong base like NaNH$$_2 in an $$acid-base reaction?

Accepted Answer

Hexane

Question 12

At physiological pH ($$pH = 7.3$$), which form of an amino acid predominates?

Accepted Answer

The zwitterionic form

Question 13

Which of the following is a Lewis acid in the reaction below?

$$\ce{H2O + BF3  H2O-BF3}$$

Accepted Answer

$$\ce{BF3}$$

Question 14

Which of the following best explains why pyruvic acid ($$pK_a = 2.5) is $$almost completely deprotonated at physiological pH ($$pH = 7.3$$)?

Accepted Answer

Because $$pH \u003e pK_a$$ for pyruvic acid, so the conjugate base is favored.

Question 15

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

Accepted Answer

The strongest base that can exist in water is OH$$^-.$$

Question 16

Which of the following is the correct expression for the equilibrium constant ($$K_{eq}) $$for the reaction:

$$\ce{A + B  C + D}$$

Accepted Answer

$$K_{eq} = \frac{[C][D]}{[A][B]}$$

Question 17

Which of the following factors does NOT stabilize a conjugate base according to the CARIO principles?

Accepted Answer

Increased negative charge

Question 18

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

Accepted Answer

A strong acid has a weak conjugate base.

Question 19

Which of the following best explains why amides are generally weaker bases than amines?

Accepted Answer

Amides have more resonance stabilization, which delocalizes the lone pair on nitrogen.

Acids and Bases in Organic Chemistry: Mechanisms, Structure, and Biological Context

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