Quiz 3 Flashcards
Identify the compound with the highest pKa.
A) CH3CH3
B) HCCH
C) CH2CH2
D) CH3OH
E) CH3NH2
A) CH3CH3
Which of the following is the strongest acid?
A) CH3OH
B) CH3OH2+
C) H2N-
D) CH3NH2
E) CH3NH3+
B) CH3OH2+
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
C) [CH3COOH] = [CH3COO-]
Write a completed equation for the acid-base pair shown below.
HCO2H + -NH2 →
HCO2H + -NH2 → HCO2- + NH3
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?
3.7
Explain why : NF3 is a weaker base than : NH3.
Fluorine has an electron withdrawing effect that reduces the availability of the pair of electrons on nitrogen. Thus the basicity of : NF3 is less than that of : NH3.
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.
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.
Which of the following is the strongest acid?
A) HF
B) H2O
C) : NH3
D) CH4
E) CH3OH
A) HF
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 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
B) water; CH3(CH2)4CO2-
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.
At what pH will 25% of a compound with a pKa of 5.3 be in its basic form?
4.8
Which of the following is not a conjugate acid-base pair?
A) H2O, HO-
B) H2O, H3O+
C) HSO4-, H2SO4
D) -OH, O2-
E) NO3-, NO2-
E) NO3-, NO2-
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
C) ether; CH3(CH2)4CO2H
HCN has a pKa = 9.1. What form of the compound, HCN or CN-, will predominate in a solution of pH = 7.0
HCN
A) CH3CH2OH
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
E) At pH = 5.5, the solution contains about 90% A- and 10% H-A
2-Propanol is shown below. Draw the structure of its conjugate base.
(CH3)2CHOH
Give the conjugate acid and the conjugate base for HSO4-.
Answer: conjugate acid: H2SO4
conjugate base: SO42-
Explain why AlCl3 is a Lewis acid.
A Lewis acid is an electron pair acceptor. Aluminum in AlCl3 has an empty p orbital that can accommodate the pair of electrons provided by a Lewis base.
E) V
Identify the most acidic carboxylic acid.
A) ICH2COOH
B) BrCH2COOH
C) CH3COOH
D) FCH2COOH
E) ClCH2COOH
D) FCH2COOH
What is the conjugate base of CH3NH2?
A) CH3NH3+
B) CH3NH-
C) NH4+
D) NH2-
B) CH3NH-
What is the conjugate acid of NH3?
A) +NH3
B) -NH
C) +NH4
D) -NH2
E) +NH2
C) +NH4
What is the conjugate acid of CH3NH2?
A) CH3NH3+
B) CH3NH-
C) NH4+
D) NH2-
A) CH3NH3+
