Deck 2: Acids and Bases: Central to Understanding Organic Chemistry

Question 1

Which of the following is the strongest acid?

A)CH₃CH₂OH
B)CH₃OCH₃
C)CH₃-NH-CH₃
D)CH₃-C CH
E)CH₃-CH CH₂

Answer 1

CH₃CH₂OH

Question 2

Which of the following is not a conjugate acid-base pair?

A)"H₂O, HO^-"
B)"H₂O, H₃O⁺"
C)"HSO₄^-, H₂SO₄"
D)"^-OH, O^2-"
E)"NO₃^-, NO₂^-"

Answer 2

"NO₃^-, NO₂^-"

Question 3

Which of the following ions is the strongest acid?

A)H^-
B)HO^-
C)HSO₄^-
D)H₂O
E)H₃O⁺

Answer 3

H₃O⁺

Question 4

Which of the following is the strongest acid?

A)HF
B)H₂O
C): NH₃
D)CH₄
E)CH₃OH

Question 5

What is the conjugate acid of CH₃NH₂?

A)CH₃NH₃⁺
B)CH₃NH^-
C)NH₄⁺
D)NH₂^-

Question 6

Which species act as bases in the following reaction?

A)1 and 2
B)3 and 4
C)2 and 4
D)1 and 3
E)2 and 3

Question 7

2-Propanol is shown below. Draw the structure of its conjugate base.
(CH₃)₂CHOH

Question 8

What is the pH of a 0.1 M solution of HCl? (Note: pK_a for HCl is -6.)

A)6
B)-6
C)1
D)-8
E)-1

Question 9

Identify the compound with the highest pK_a.

A)CH₃CH₃
B)HCCH
C)CH₂CH₂
D)CH₃OH
E)CH₃NH₂

Question 10

What is the conjugate base of CH₃NH₂?

A)CH₃NH₃⁺
B)CH₃NH^-
C)NH₄⁺
D)NH₂^-

Question 11

Consider the set of compounds, NH₃, HF, and H₂O. Rank these compounds in order of increasing acidity and discuss your rationale.

Question 12

Which of the following is the strongest acid?

A)CH₃OH
B)CH₃OH₂⁺
C)H₂N^-
D)CH₃NH₂
E)CH₃NH₃⁺

Question 13

Give the conjugate acid and the conjugate base for HSO₄^-.

Question 14

If H₂O has a pK_a value of 15.7 and HF has a pK_a value of 3.2, which is a stronger base, HO^- or F^-? Explain.

Question 15

Identify the compound with the highest pK_a.

A)CH₃NH₂
B)CH₃OH
C)CH₃COOH
D)H₂O
E)CH₃NH₃⁺

Question 16

What is the product formed from the following acid-base reaction when ammonia functions as a base? The equilibrium lies far to the reactants.

A)CH₃O^- + ⁺NH₄
B)CH₂OH + ⁺NH₃
C)CH₃OH₂⁺ + ^-NH₂
D)CH₃NH₂ + H₂O
E)CH₄ + NH₂OH

Question 17

What is the conjugate acid of NH₃?

A)"⁺NH₃"
B)"^-NH"
C)"⁺NH₄"
D)"^-NH₂"
E)"⁺NH₂"

Question 18

The pKa of CH₃COOH is 4.8 and the pKa of HCOOH is 3.8. Given this information, one knows that ________.

A)CH₃COOH completely ionizes in water
B)HCOOH is a weaker acid than CH₃COOH
C)HCOO^- is a weaker base than CH₃COO^-
D)CH₃COOH reacts with HO^- while HCOOH does not
E)HCOOH reacts with HO^- while CH₃COOH does not

Question 19

The conjugate acid of H₂O is ________.

A)H₃O^-
B)H₃O
C)H₃O⁺
D)HO^-
E)H₂O⁺

Question 20

Write a completed equation for the acid-base pair shown below.
HCO₂H + ^-NH₂ →

Question 21

The pKa of CH₃COOH is 4.8. If the pH of an aqueous solution of CH₃COOH and CH₃COO^- is 4.8, then one knows ________.

A)CH₃COOH is completely ionized
B)[CH₃COOH] > [CH₃COO^-]
C)[CH₃COOH] = [CH₃COO^-]
D)[CH₃COOH] < [CH₃COO^-]
E)CH₃COOH is completely unionized

Question 22

Buffering is used to maintain the pH of human blood in the relatively narrow 7.3 - 7.4 range. What acid/base pair serves to buffer the blood?

A)H₂O / HO^-
B)H₃O⁺ / H₂O
C)H₂CO₃ / HCO₃^-
D)NH₄⁺ / NH₃
E)HCl / Cl^-

Question 23

At what pH will the concentration of a compound with a pKa of 5.7 be 100 times greater in its acidic form than in its basic form?

Question 24

At what pH will 25% of a compound with a pKa of 5.3 be in its basic form?

Question 25

Explain why AlCl₃ is a Lewis acid.

Question 26

Draw a resonance contributor and the resonance hybrid for HOCO₂^-.

Question 27

H-A is an acid with a pKa of 4.5. Which of the following statements about an aqueous solution of H-A is true?

A)At pH = 4.5, the solution contains much more H-A than A^-
B)At pH = 4.5, the solution contains much more A^- than H-A
C)At pH- 3.5, the solution contains about 90% A^- and 10% H-A
D)At pH = 6.5, the soluton contains about 80% A^{- and 20% H-A}
E)At pH = 5.5, the solution contains about 90% A^- and 10% H-A

Question 28

The amino acid glycine (H₃N⁺CH₂CO₂H)has two acidic Hs, one with pKa = 2.34 and the other with pKa=9.60. Draw the structure of the form of glycine that predominates at a pH of 12.

Question 29

HCN has a pKa = 9.1. What form of the compound, HCN or CN^-, will predominate in a solution of pH = 7.0

Question 30

Would you predict trifluoromethanesulfonic acid, CF₃SO₃H, to be a stronger or weaker acid than methanesulfonic acid, CH₃SO₃H? Explain your reasoning.

Question 31

Propanoic acid, CH₃CH₂COOH, has a pKa =4.9. Draw the structure of the conjugate base of propanoic acid and give the pH above which 90% of the compound will be in this conjugate base form.

Question 32

When a small amount of hexanoic acid [CH₃(CH₂)₄CO₂H, pKa~4.8], is added to a separatory funnel which contains the organic solvent diethyl ether and water with a pH of 2.0, it is found mainly in the ________ phase as ________.

A)ether; CH₃(CH₂)₄CO₂^-
B)water; CH₃(CH₂)₄CO₂^-
C)ether; CH₃(CH₂)₄CO₂H
D)water; CH₃(CH₂)₄CO₂H
E)none of the above

Question 33

Identify the most acidic carboxylic acid.

A)ICH₂COOH
B)BrCH₂COOH
C)CH₃COOH
D)FCH₂COOH
E)ClCH₂COOH

Question 34

Which of the following is the strongest acid?

A)I
B)II
C)III
D)IV
E)V

Question 35

When a small amount of hexanoic acid [CH₃(CH₂)₄CO₂H, pK_a~4.8], is added to a separatory funnel which contains the organic solvent diethyl ether and water with a pH of 12.0, it is found mainly in the ________ phase as ________.

A)ether; CH₃(CH₂)₄CO₂^-
B)water; CH₃(CH₂)₄CO₂^-
C)ether; CH₃(CH₂)₄CO₂H
D)water; CH₃(CH₂)₄CO₂H
E)none of the above

Question 36

Explain why : NF₃ is a weaker base than : NH₃.

Question 37

Which of the following anions, CH₃CHBrCO₂^- or CH₃CHFCO₂^- is the stronger base? Explain your choice.