CHEM 132.197
EXAM Ch.16-18
Key begins on page 5.
1. A 0.100 M solution of a weak monoprotic acid has a pH of 2.30. What is the equilibrium constant, Ka, for
this acid?
Ka = ___________________
2. What is the pH in a titration when 20.0 mL of 0.0150 M KOH has been added to 35.0 mL 0f 0.0100 M HCl?
(Note that the resulting salt is neutral)
a) 2.86
b) 2.92
c) 3.04
d) 3.18
e) 3.92
3. What is the pH of a 0.03 M solution of benzoic acid? (Ka = 6.3 x 10-5)
pH = ____________
Use the following information for questions 4 and 5. Carbonic acid is a diprotic acid, H2CO3, with
Ka1 = 4.2 x 10-7 and Ka2 = 4.8 x 10 -11.
4. What is the [HCO3-1] concentration in a 0.037 M H2CO3 solution?
[HCO3-1] = _________________
5. What is the carbonate ion, CO3-2, concentration in a 0.037 M carbonic acid solution?
a) 1.2 x 10-4
b) 4.2 x 10-7
c) 7.6 x 10-8
d) 4.8 x 10-11
e) 5.2 x 10-19
6. Using the equilibrium constants at 25oC from the table,
HCN(aq)
H2O(l)
H+(aq) + CN-1(aq)
H+(aq) + OH-1 (aq)
K = 4.9 x 10-10
K = 1.0 x 10-14
calculate the K at 25oC for the following reaction.
HCN(aq) + OH-1(aq)
CN-1(aq) + H2O(l)
K = __________________________
7. What is the pH of a solution that is 0.100 M in acetic acid acid and 0.50 M in sodium acetate?
(Ka = 1.8 x 10-5)
a) 0.70
b) 2.87
c) 4.05
d) 4.74
e) 5.44
8. In titrating 0.20 M acetic acid, HC2H3O2, with 0.20 M NaOH, the solution at the equivalence point is
a) 0.20 M NaC2H3O2
b) neutral
c) slightly acidic
d) 0.10 M HC2H3O2 and 0.10 M NaOH
e) 0.10 M NaC2H3O2
Questions 9-12 are concerned with the titration of propionic acid.
9. A 25.00 mL sample of propionic acid, HC3H5O2, of unknown concentration was titrated with 0.104 M KOH.
The equivalence point was reached when 35.31 mL of the base had been added. The concentration of the
original propionic acid is:
a) 0.0736 M
b) 0.128 M
c) 0.147 M
d) 0.162 M
e) 0.295 M
10. What is the concentration of the propionate ion, C3H5O2-1 , at the equivalence point?
11. If the Ka for propionic acid is 1.34 x 10-5, what is the Kb for the propionate anion, C3H5O2-1?
12. What is the pH at the equivalence point of this titration?
13. 1.0 M solutions of the following three salts: NaF
are, respectively
a) basic, neutral, and acidic
b) basic, acidic, and acidic
c) acidic, acidic, and neutral
Al(NO3)3
NH4NO3
will result in solutions that
d) acidic, basic, and basic
e) acidic, acidic, and neutral
14. The molar solubility of AgSCN is 1.0 x 10-6. What is the Ksp for AgSCN?
Ksp = ________________
15. A saturated solution of PbBr2 is prepared by dissolving the solid salt in water. The concentration of Br-1 ion
in solution is found to be 0.023M. Calculate the Ksp for PbBr2.
Ksp = _______________
16. The Ksp of Cd(OH)2 is 1.20 x 10-14. What is the pH of a saturated solution of cadmium hydroxide?
a) 4.5
b) 4.8
c) 9.2
d) 9.5
e) 9.7
17. The Ksp for AgI is 1.0 x 10-16. If you mix 500 mL of 1.0 x 10-8 M AgNO3 with 500 mL of 1.0 x 10-8 M NaI,
then:
a) AgI will precipitate.
b) no precipitation will occur.
c) 1.0 x 10-8 moles of AgI will form.
d) silver nitrate will precipitate.
e) sodium nitrate will precipitate.
18. What is the molar solubility of MgF2 in a 0.200 M NaF solution? (Ksp for MgF2 is 8.0 x 10-8)
19. A solution that is 0.0010 M in Fe+2, Cd+2, Co+2, and Mn+2 is saturated with H2S resulting in a [S-2]
concentration of 1.10 x 10-15. Which metals will form a precipitate? (The Ksp values are FeS = 6 x 10-18,
CdS = 8 x 10-27 , and MnS = 2.5 x 10-10)
a) MnS
b) MnS and FeS
c) CdS and CoS
d) CdS, FeS, and CoS
e) FeS, CdS, CoS, and MnS
20. What is the concentration of Cd+2(aq) ion in a 0.010 M Cd(NO3)2 solution that is also 1.00 M in NH3?
( The Kf for Cd(NH3)4+2 is 1.00 x 107)
[Cd+2] = ___________________
21. The heat of vaporization of freon, CCl2F2, is 17.2 kJ/mol at 25oC. What is the change in entropy for one
mole of liquid freon when it vaporizes at 25oC?
a) 57.7 J/K
b) 0.688 J/K
c) 5.13 x 10-3 J/K
d) 3.16 J/K
e) 2.39 J/K
22. Which one of the following processes would be expected to have a positive ∆S value?
a) N2(g) + 3 H2(g)
b) H2O(l)
c)
2 NH3(g)
d) CaCO3(s)
H20(g)
Cl2(g) + Br2(g)
23. For the following reaction at 25oC,
CaO(s) + CO2(g)
e) 2 NO(g) + O2(g)
2 NO2(g)
2 ClBr(g)
I2(g) + Cl2(g)
2 ICl(g)
∆Ho = -26.9 kJ and ∆So = 11.3 J/K. Calculate ∆Go for the reaction in kJ.
∆Go = __________________
o
24. If a reaction is exothermic and nonspontaneous at 25 C then it:
a) can never be spontaneous.
b) can become spontaneous by adding a catalyst.
c) may be spontaneous at higher temperatures.
25. For the following process, Br2(l)
d) may be spontaneous at lower temperatures.
e) is endothermic and spontaneous at high temperatures
Br2(g)
a) ∆H is (+) and ∆S is (-) for the reaction.
b) ∆H is (-) and ∆S is (-) for the reaction.
c) ∆H is (+) and ∆S is (+) for the reaction.
d) ∆H is (-) and ∆S is (+) for the reaction.
e) ∆G is (+) for all temperatures.
26. What is the minimum temperature required for the spontaneous conversion of one mole of CCl4(l) to CCl4(g)
when ∆Ho is 573 kJ and ∆So is 1.64 kJ/K?
27. For the reaction 3 C(s) + 4 H2(g)
C3H8(g), ∆So is -269 J/K and ∆Ho is 103.8 kJ/mol
Calculate the equilibrium constant at 25oC for the reaction.