SUNY College @ Oneonta
Chem. 112: Spring 2011 Exam 3A
Odago/04-28-2011
Attempt all questions and fill in your answers correctly (dark enough) on the scatron using pencils.
1.
Which of the following species cannot act as a Lewis acid?
a. K+
b. Mg2+
c. Al3+
d. H+
e. H–
2.
The acid strength decreases in the series HBr > HSO4– > CH3COOH > HCN > HCO3–. Which of the following is the
strongest conjugate base?
a. CO32–
b. CN–
c. CH3COO–
d. SO42–
e. Br–
3.
Which solution has the highest pH? Given that the relative strengths of the acids is HClO4 > HI > HBr > HCl > HF
a. 0.10 M HF (aq)
b. 0.10 M HCl (aq)
c. 0.10 M HBr (aq)
d. 0.10 M HI (aq)
e. 0.10 M HClO4 (aq)
The ionization constant of water at a temperature above 25°C is 3.3 × 10-14. What is the pH of pure water at this
temperature?
2H2O(l)
H3O+(aq) + OH–(aq)
a. 13.52
b. 6.74
c. 7.00
d. 7.74
e. 5.54
4.
5.
6.
What is the pH of a solution prepared by dissolving 0.832 g of NaOH(s) (Molar Mass = 40 g/mol) in 6.50 L of water?
a. 2.495
b. 12.318
c. 1.682
d. 7.000
e. 11.505
The pOH of a solution is 5.30. What is its hydronium-ion concentration [H3O+]?
a.
b.
c.
d.
e.
7.
5.30 M
5.0 × 10–6 M
2.0 × 10–9 M
5.0 × 10–3 M
2.0 × 105 M
Rank acetic acid (HC2H3O2), hydrocyanic acid (HOCN), and hydrofluoric acid (HF) in order of increasing strength.
Acid
HC2H3O2
HOCN
HF
pKa
4.74
3.46
3.17
a)
b)
c)
d)
e)
HC2H3O2 < HOCN < HF
HOCN < HC2H3O2 < HF
HF < HOCN < HC2H3O2
HF < HC2H3O2 < HOCN
HOCN < HF < HC2H3O2
1
8.
A 0.10 M aqueous solution of a weak acid HA has a pH of 4.00. What is the value of Ka for HA?
a.
b.
c.
d.
e.
9.
H3PO4 is a ________ acid, H3PO4 is a ________ acid than H2PO4–, and H2PO4– is a__________ acid than HPO42–.
a.
b.
c.
d.
e.
10.
11.
1.0 × 10-8
1.0 × 10-7
1.0 × 10-6
1.0 × 10-5
1.0 × 10-4
strong, stronger, stronger
weak, weaker, weaker
weak, stronger, stronger
strong, weaker, weaker
strong, weaker, stronger
What is the pH of a 0.035 M solution of benzoic acid (Ka = 6.3 × 10-5) at 25ºC? {benzoic acid is a weak acid}
a. 6.51
b. 2.83
c. 5.66
d. 5.20
e. 1.46
What is the base-ionization equilibrium constant for an aqueous solution of ammonia, NH3?
a.
Kb =
[OH − ][NH 4 + ]
[NH3 ]
b.
Kb =
[H + ][NH3 ]
[NH 4 + ]
c.
Kb =
[OH − ][NH3 ]
[NH 4 + ]
d.
[NH 4 + ]
Kb =
[NH3 ][OH − ]
e.
None of these.
12.
What is the pOH of a 0.19 M solution of pyridine (Kb = 1.4 × 10-9) at 25ºC? {pyridine is a weak base}
a.
11.02
b.
4.79
c.
8.85
d.
4.07
e.
1.44
13.
What is the solubility product expression for Zn3(PO4)2?
a.
Ksp = [Zn32+][(PO43–)2]
b.
Ksp = [Zn2+][2PO43–]
c.
Ksp = [Zn2+]3[PO43–]2
d.
Ksp = [3Zn2+]3[2PO43–]2
e.
Ksp = [Zn3+]2[PO42–]3
2
14.
What is the hydroxide-ion concentration of a saturated solution of Cu(OH)2? Given that for Cu(OH)2, Ksp = 2.6 × 10–19.
a. 4.0 × 10–7 M
b. 8.0 × 10–7 M
c. 5.1 × 10–10 M
d. 1.1 × 10–5 M
e. 1.0 × 10–7 M
15. Which of the following statements are characteristic of acids?
1. They turn blue litmus red.
2. They neutralize bases.
3. They increase the pH of aqueous solutions.
a. 1 only
b. 2 only
c. 3 only
d. 1 and 2 only
e. 1, 2, and 3
16. A saturated solution of Fe(OH)2 has a pH of 9.4. Calculate the Ksp for Fe(OH)2
a. 1.9 x10-15
b. 3.9 x10-15
c. 1.5 x10-14
d. 8.0 x10-30
e. 7.9 x10-15
17. According to Bronsted-Lowry definition, a base is
a.
b.
c.
d.
e.
A substance that increases the hydroxide ion concentration in water
A substance that can accept a proton from an acid
A substance that can donate an electron pair to the formation of a covalent bond
A substance that increases the anion concentration by the autoionization of the solvent
None of these
18. A solution where [H3O+]=10-13M is ___________
a. Basic
b. Neutral
c. Acidic
d. Strongly acidic
e. Amphoteric
19. What is the pH of a 2.0 M solution of HClO4? (a strong monoprotic acid)
a. 13.70
b. 0.30
c. -0.30
d. 14.30
e. Minus infinity
20. Which of the following is true for a buffered solution?
a. The solution resists any changes in its [H+].
b. The solution will not change its pH very much if a concentrated acid is added.
c. The solution will not change its pH very much if a strong base is added.
d. Any H+ ions added will react with a conjugate base of a weak acid already in solution.
e. All of these
21. Ammonium nitrate, NH4NO3, is administered as an intravenous solution to patients whose blood pH has deviated from
the normal value of 7.40. Would this substance be used for acidosis (blood pH < 7.40) or alkalosis (blood pH > 7.40)?
3
a.
b.
c.
d.
e.
It doesn’t matter since blood is a buffer
Acidosis patient
Alkalosis patient
None of the above
It doesn’t matter since NH4NO3 is a neutral salt.
22.
What is the pH of a 0.0041 M Ba(OH)2 solution? (Barium hydroxide is a strong base)
a. 2.09
b. 11.61
c. 2.39
d. 9.20
e. 11.91
23.
What is the pH of a solution that is 0.040 M in HA and also 0.0024 M in NaA? (Ka = 4.4 × 10-6)
a. 6.58
b. 4.13
c. 5.36
d. 7.52
e. 8.06
24.
For which of the following will precipitation be expected?
a. Qc > Ksp
b. Qc < Ksp
c. Qc = Ksp
d. Qc = 1
e. Ksp = 1
25.
What is the molar solubility of silver(I) acetate at 25ºC? The solubility product constant for silver(I) acetate is 2.0 ×
10–3 at 25ºC. (silver (I) acetate = AgCH3CO2)
a. 2.0 × 10–3 M
b. 1.0 × 10–3 M
c. 1.1 × 10–1 M
d. 7.9 × 10–2 M
e. 4.5 × 10–2 M
26.
The insoluble salts AV, B2W, C2X3, DY2, and EZ3, which were formed from the metal ions A+, B+, C3+, D2+, and E3+
and the nonmetals V1–, W2–, X2–, Y1–, and Z1–, all have the same Ksp value. Which salt has the highest molar solubility?
a. AV
b. B2W
c. C2X3
d. DY2
e. EZ3
27.
Which of the following solutions has the highest hydroxide-ion concentration?
a. 0.1 M HCl
b. 0.1 M H2SO4
c. a buffer solution with pH = 5
d. a buffer solution with pOH = 12
e. pure water
28.
A weak base is titrated with a hydrochloric acid solution. What is the pH at the equivalence point?
a. less than 7
b. equal to 7
c. greater than 7
d. equal to pKa
e. equal to pKb
4
29.
A solution in which the pOH is 12.5 would be described as
a.
b.
c.
d.
e.
30.
very acidic.
slightly acidic.
neutral.
very basic.
slightly basic.
The titration curve shown below represents the titration of a weak acid with a strong base. Which point represents the
equivalence point?
a. I
b. II
c. III
d. IV
e. V
_________________________________________________ END ______________________________________________
RELEVANT EQUATIONS
pH = − log [H3O+]
pH + pOH = 14
[H3O+] = 10−pH
Ka =
Kw = [H3O+][OH−] = 1.00 x 10−14 (at 250C)
Kb = KaKb=Kw
Henderson-Hasselbalch equation
pH = pKa + log
[A - ]
[HA]
pH = − log Ka + log
[H 3 O + ] [A - ]
[HA]
HB
OH
B
or simply as
[buff. base]
[buff. acid]
5