1. No category

Sample Exam #2
1. A 0.10M aqueous solution of a weak acid HA has a measured pH of 5.00. What is the value of Ka
for this weak acid?
a. 1.0 x 10-9
b. 1.0 x 10-5
c. 1.0 x 10-6
d. 1.0 x 10-1
e. 1.0 x 10-11
2. What is the pH of a 0.010 M solution HBrO, which has a Ka = 2.5 x 10-9?
a. 5.30
b. 8.70
c. 8.60
d. 5.40
e. 3.70
3. The pH of a 0.15M solution of an unknown weak base is 11.28. What is the pKb of this weak base?
a. 2.72
b. 21.74
c. 0.82
d. 4.61
e. none of the above
4. When each is dissolved in water, which of the following salts will form an acidic solution?
a. Fe(NO3)3
b. NaClO
c. CH3NH3Cl
d. both a and c e. none of these
5. What is the pH of a 0.10M solution of NaF? The Ka for HF is 3.5 x 10-4.
a. 8.23
b. 5.77
c. 2.23
d. 11.77
e. none of the above
6. What is the pH of a 0.25M solution of the salt C2H5NH3Cl? The Kb for C2H5NH2 is 5.6 x 10-4.
a. 1.93
b. 12.07
c. 8.32
d. 5.68
e. none of the above
7. Which of the following pairs of acids is incorrectly ordered (stronger to weaker)?
a. HCl > HF
b. HClO > HBrO
c. HBrO3 > HBrO
d. HIO4 > HClO4
e. both b and c are incorrect
8. What is the pH of a solution made by adding 25.0mL of 0.050M HCl to 75.0mL of 0.10M HClO?
The Ka for HClO is 2.9 x 10-8.
a. 1.30
b. 1.90
c. 4.33
d. 6.76
e. none of the above
9. What is the pH of a solution made by adding 15.0mL of 0.080M NH3 to 45.0mL of 0.10M NH4Br?
The Kb for NH3 is 1.8 x 10-5.
a. 9.16
b. 8.68
c. 9.83
d. 5.32
e. none of the above
10. What is the pH of a buffer solution that contains 0.050M HF and 0.15M NaF? The Ka for HF is 3.5
x 10-4.
a. 3.46
b. 3.93
c. 2.98
d. 2.38
e. none of the above
11. A solution of HF is partially titrated by adding 250mL of a 0.10M NaOH solution to 750mL of a
0.10M HF solution. If Ka for HF is 3.5 x 10-4, then what is the resulting pH?
a. 3.46
b. 3.15
c. 2.98
d. 3.76
e. none of the above
12. To 100mL of a buffer solution that is 0.10M in both HCHO2 and NaCHO2, we add 0.0020 moles of
HCl. What will be the pH of the buffer after the addition of the strong acid? Assume that the
volume change is negligible and Ka for HCHO2 is 1.7 x 10-4.
a. 3.77
b. 3.17
c. 3.59
d. 1.70
e. none of the above
13. If you mix 0.10 mol of NaOH with 0.10 mol of HC2H3O2 in 1.0 L of water, you will have a solution
that is
a. neutral, pH = 7
b. slightly acidic, pH between 2 and 7
c. slightly basic, pH between 7 and 12
d. very acidic, pH less than 2
e. very basic, pH greater than 12
14. What is the pH of a 0.075M solution of NaHC2O4? The Ka1 and Ka2 for H2C2O4 are 6.0 x 10-2 and
6.1 x 10-5.
a. 2.67
b. 1.17
c. 7.05
d. 11.33
e. none of the above
15. A 25.0mL sample of a 0.200M HCHO2 solution is titrated with 0.100M NaOH. What is the pH of
the solution at the endpoint? The Ka for HCHO2 is 1.8 x 10-4.
a. 7.00
b. 10.26
c. 5.48
d. 8.52
e. 8.28
16. The molar solubility for PbI2 is 1.3 x 10-3 M. Calculate the value of Ksp for PbI2.
a. 1.7 x 10-6
b. 4.4 x 10-9
c. 8.8 x 10-9
d. 6.9 x 10-2
e. none of the above
17. What is the concentration of Ag+ in a saturated solution of Ag3PO4? The Ksp for this compound is
1.8 x 10-18.
a. 1.6 x 10-5 M
b. 4.8 x 10-5 M
c. 1.3 x 10-9 M
d. 2.0 x 10-3 M
e. 3.7 x 10-5 M
18. What is the molar solubility of MgF2 in 0.080M NaF? The Ksp for MgF2 is 5.16 x 10-11.
a. 8.1 x 10-9 M
b. 2.3 x 10-4 M
c. 6.4 x 10-10 M
d. 9.0 x 10-5 M
e. 3.3 x 10-13 M
19. The Ksp for AgI is 1.0 x 10-16. If you mix 500.mL of 1 x 10-8 M Ag+ with 500.mL of 1 x 10-8 M I-,
then
a. AgI will precipitate
b. no precipitate forms as Q is less than K
c. 1 x 10-8 moles of AgI will form
d. a saturated solution will form as Q = K
e. a and c are true
20. What is the minimum pH required to precipitate Co(OH)2 when a 0.0050M Co+2(aq) is treated with
NaOH? The Ksp for Co(OH)2 is 5.9 x 10-15.
a. 7.73
b. 11.93
c. 5.96
d. 8.04
e. none of the above
21. What is the concentration of the Cd+2 ion in a solution that is 0.010M Cd(NO3)2 and 1.0M NH3? Kf
for Cd(NH3)4+2 is 1.0 x 107.
a. 5.6 x 10-3 M
b. 1.2 x 10-9 M
c. 7.2 x 10-12 M
d. 1.0 x 10-2 M
e. 1.0 x 10-5 M
22. What is the molar solubility of HgS(s) in a 0.50M KI solution? The Ksp for HgS is 1.6 x 10-54
and the Kf for HgI4-2 is 1.0 x 1030. The relevant reactions are:
HgS(s)  Hg+2(aq) + S-2(aq)
Hg+2(aq) + 4I-(aq)  HgI4-2(aq)
a. 3.2 x 10-13M
b. 2.8 x 10-13M
c. 1.0 x 10-29M
d. 1.6 x 10-24M
e. none of the above
23. A reaction is known to be spontaneous below about 450K and non-spontaneous above this
temperature. What are the signs for H and S, respectively, for this reaction?
a. +, +
b. +, -
c. -, -
d. -, +
e. not enough info
24. Which of the following substances would have the highest absolute entropy at 25oC?
a. Fe(s)
b. Ar(g)
c. C6H6(l)
d. Fe2O3(s)
e. NO2(g)
25. In which of the following would you predict that S would be positive?
a. I2(g)  I2(s)
b. N2(g) + 3 H2(g)  2 NH3(g)
c. 2 BrCl(g)  Cl2(g) + Br2(l)
d. all of the above should have a positive change
e. none of the above should have a positive change
26. The H and S values for a certain reaction are 30.0 kJ/mol and 60.0 J/K, respectively. Above or
below what temperature will the reaction be spontaneous?
a. < 500K
b. > 500K
c. > 0.500K
d. > 1800K
e. < 1800K
27. Given the reaction below and the Gfo’s, determine the equilibrium constant for this reaction.
PbCO3(s)  PbO(s) + CO2(g)
Gfo = -625.5 kJ
a. 0.98
-187.9 kJ
b. 2.7 x 10-8
-394.4 kJ
c. 3.7 x 107
d. 2.7 x 1017
e. none of the above
28. Find the Gfo for Al(OH)3(s) by using the Ksp for Al(OH)3 = 4.6 x 10-33 and the Gfo for the ions,
Al+3 = -481.2 kJ/mol and OH- = -157.3 kJ/mol.
Al(OH)3(s)  Al+3(aq) + 3 OH-(aq)
a. 184.4 kJ
b. 175.1 kJ
c. -1137.5 kJ
d. 822.9 kJ
e. none of the above
Answer Key: 1A, 2A, 3D, 4D, 5A, 6D 7D, 8B, 9B, 10B, 11B, 12C, 13C, 14A, 15E, 16C, 17B, 18A,
19B, 20D, 21B, 22A, 23C, 24E, 25E, 26B, 27B, 28C
Please let me know if there are any discrepancies!