Organic Chemistry 7th Edition Bruice Test Bank
Organic Chemistry 7th Edition Bruice Test Bank
Organic Chemistry 7th Edition Bruice Test Bank
Test Bank
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Organic Chemistry 7th Edition Bruice Test Bank
2) 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
Answer: A
Section: 2-1
A) 1 and 2
B) 3 and 4
C) 2 and 4
D) 1 and 3
E) 2 and 3
Answer: C
Section: 2-1
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9) Give the conjugate acid and the conjugate base for HSO4-.
Answer: conjugate acid: H2SO4
conjugate base: SO42-
Section: 2-1
10) Write a completed equation for the acid-base pair shown below.
HCO2H + -NH2 →
11) What is the pH of a 0.1 M solution of HCl? (Note: pKa for HCl is -6.)
A) 6
B) -6
C) 1
D) -8
E) -1
Answer: C
Section: 2-2
12) If H2O has a pKa value of 15.7 and HF has a pKa value of 3.2, which is a stronger base, HO-
or F-? Explain.
Answer: HO- is a stronger base than F- because HF is a stronger acid than H2O, and the
stronger the acid the weaker its conjugate base.
Section: 2-2
13) 2-Propanol is shown below. Draw the structure of its conjugate base.
(CH3)2CHOH
Answer:
Section: 2-3
3
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14) Which of the following is the strongest acid?
A) CH3OH
B) CH3OH2+
C) H2N-
D) CH3NH2
E) CH3NH3+
Answer: B
Section: 2-6
15) 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
Answer: C
Section: 2-6
4
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18) Consider the set of compounds, NH3, HF, and H2O. Rank these compounds in order of
increasing acidity and discuss your rationale.
Answer: NH3 < H2O < HF
When determining relative acidity, it is often useful to look at the relative basicity of the
conjugate bases. The stronger the acid, the weaker (more stable, less reactive) the conjugate base.
In this case, one would look at the relative basicity of F-, OH-, and NH2-. The relative strengths
of these species can be gauged based on the electronegativity of the charged atom in each base.
Since fluorine is the most electronegative, F- is the most stable, least reactive base in the group.
This means that its conjugate acid, HF, is the strongest.
Section: 2-6
5
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22) Which of the following is the strongest acid?
A) I
B) II
C) III
D) IV
E) V
Answer: E
Section: 2-7
24) Would you predict trifluoromethanesulfonic acid, CF3SO3H, to be a stronger or weaker acid
than methanesulfonic acid, CH3SO3H? Explain your reasoning.
Answer: Trifluoromethanesulfonic acid is a stronger acid. Compare the strengths of the
conjugate bases and remember that the weaker the base, the stronger the conjugate acid. In the
case of the trifluoro derivative, the presence of the highly electronegative fluorine atoms serves
to delocalize the negative charge to a greater extent. This additional delocalization makes
trifluoromethanesulfonate a weaker base.
Section: 2-7
25) Which of the following anions, CH3CHBrCO2- or CH3CHFCO2- is the stronger base?
Explain your choice.
Answer: CH3CHBrCO2- is the stronger base. The more electronegative F atom can more
effectively delocalize the negative charge via induction. This greater delocalization stabilizes
CH3CHFCO2- relative to CH3CHBrCO2- and makes it a weaker base.
Section: 2-7
6
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26) Draw a resonance contributor and the resonance hybrid for HOCO2-.
Answer: resonance contributor: resonance hybrid:
Section: 2-8
27) 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
Answer: C
Section: 2-10
7
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30) At what pH will 25% of a compound with a pKa of 5.3 be in its basic form?
Answer: 4.8
Section: 2-10
31) 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.
Answer:
Section: 2-10
32) 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
Answer: E
Section: 2-10
33) 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?
Answer: 3.7
Section: 2-10
34) HCN has a pKa = 9.1. What form of the compound, HCN or CN-, will predominate in a
solution of pH = 7.0
Answer: HCN
Section: 2-10
35) 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.
Answer: CH3CH2COO-; 5.9
Section: 2-10
8
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Organic Chemistry 7th Edition Bruice Test Bank
36) 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-
Answer: C
Section: 2-11
9
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