1.
[7 points] The solubilty of manganese (II) hydroxide is 2.2 × 10-5 M. What is
the Ksp of Mn(OH)2?
a.
b.
c.
d.
e.
2.
[7 points] What is the molar solubility of PbCl2 in a 0.15 M solution of HCl?
The Ksp of PbCl2 is 1.6 × 10-5?
a.
b.
c.
d.
e.
3.
H2O
0.5 M HI solution
0.2 M HI solution
1.0 M HNO3 solution
0.8 M KI solution
[7 points] Which of the following substances will decrease the solubility of
Pb(OH)2 in a saturated solution?
a.
b.
c.
d.
e.
5.
2.0 × 10-3 M
1.1 × 10-4 M
1.8 × 10-4 M
7.1 × 10-4 M
1.6 × 10-5 M
[7 points] In which aqueous system is PbI2 least soluble?
a.
b.
c.
d.
e.
4.
1.1 × 10-14
4.3 × 10-14
2.1 × 10-14
4.8 × 10-10
2.2 × 10-5
NaNO3
H2O2
HNO3
Pb(NO3)2
NaCl
[7 points] How many grams of Ag2SO4 (formula weight = 312 g/mol) will
dissolve in 1.5 L of water (Ksp = 1.5 × 10-5)?
a.
b.
c.
d.
e.
1.6 × 10-2
3.9 × 10-3
4.9 g
7.3 g
1.8 g
6.
[7 points] To what final concentration of NH3 must a solution be adjusted to
just dissolve 0.15 mol of NiC2O4 (Ksp = 4 × 10-10) in 1.0 L of solution? The
formation constant for the formation of Ni(NH3)62+ is Kf = 1.2 × 109.
a.
b.
c.
d.
e.
7.
2.7 × 10-9 M
4.7 × 10-2 M
0.27 M
4.7 × 10-4 M
None of the above
[7 points] You have a saturated solution of silver acetate (AgC2H3O2). Which
of the following substances will increase the solubility of silver acetate?
AgNO3
a.
b.
c.
d.
e.
8.
NaC2H3O2
NH3
HNO3 & NH3
AgNO3 and NaC2H3O2
HNO3
NaC2H3O2 and NH3
All of the above will increase the solubility of AgC2H3O2
[7 points] A solution is 0.10 M NaBr and 0.10 M NaCl. If solid AgNO3 is added
to the solution what is the concentration of Br- ions when AgCl (Ksp = 1.8 × 10-10)
begins to precipitate? (AgBr Ksp = 5.0 × 10-13)
a.
b.
c.
d.
e.
9.
HNO3
1.3 × 10-5
3.0 × 10-3
5.0 × 10-12
1.8 × 10-9
2.7 × 10-4
[7 points] Which of the following descriptions best describes the behavior of
an amphoteric hydroxide (i.e. Al(OH)3) in water?
a.
b.
c.
d.
e.
It dissolves upon addition of concentrated NaOH solution
It dissolves upon addition of concentrated HCl solution
It precipitates when concentrated NaOH solution is added
It precipitates when concentrated HCl solution is added
It dissolves when either concentrated HCl or NaOH solution is added
10. [7 points] A solution of NaF is added dropwise to a solution that is 0.0144 M in
Ba2+. BaF2 (Ksp = 1.7 × 10-6) will begin to precipitate when the concentration of
F- ions reaches what value? Neglect volume changes associated with the
addition of the NaF solution.
a.
b.
c.
d.
e.
5.9 × 10-5
1.1 × 10-2
2.4 × 10-8
2.7 × 10-3
1.2 × 10-4
11. [7 points] A solid sample could contain any or all of the following: Pb(NO3)2,
AgNO3, NaCl. When sufficient water was added to dissolve the sample a white
precipitate formed. The precipitate dissolved when the solution was heated,
but the precipitate reformed when the solution cooled back to room
temperature. A final test was made by adding concentrated NH3, but this had
no perceivable effect on the precipitate. What substances were present in the
original sample?
a.
b.
c.
d.
e.
Pb(NO3)2 only
AgNO3 only
Pb(NO3)2 and NaCl
AgNO3 and NaCl
Pb(NO3)2 and AgNO3
12. [7 points] What color is SnS2?
a.
b.
c.
d.
e.
black
red
orange
yellow
white
13. [7 points] What reagent(s) could be used to separate Sn4+ and Ni2+?
a.
b.
c.
d.
e.
HCl
HNO3
Thioacetamide, CH3CSNH2 and heat
Thioacetamide, CH3CSNH2, HNO3 and heat
NaOH
A sample containing only group III cations was analyzed according to the group III
procedure followed in our lab. Treatment with NH4/NH3 buffer produced a dark
precipitate (ppt A) and a colorless solution (sol’n B). Ppt A was treated with NaOH
and H2O2, which caused the precipitate to partially dissolve, and the solution to turn
yellow. Given these observations we can classify each of the six group III cations
as either definitely present, definitely absent or undetermined. Use these
classification to answer questions 14-16.
14. [7 points] Which ions are definitely present?
a.
b.
c.
d.
e.
Zn2+ and Cr3+
Fe3+
Cr3+
Fe3+ and Cr3+
Zn2+, Fe3+ and Cr3+
15. [7 points] Which ions are definitely absent?
a.
b.
c.
d.
e.
Al3+
Ni2+ and Co2+
Al3+ and Zn2+
Al3+, Ni2+ and Co2+
Zn2+, Fe3+ and Cr3+
16. [7 points] Which ions are undetermined, given the above observations?
a.
b.
c.
d.
e.
Zn2+ and Al3+
Al3+
Cr3+
Zn2+
Zn2+ and Cr3+
17. [7 points] Which of the following substances are amphoteric?
a.
b.
c.
d.
e.
CuS
PbS
Al(OH)3
Fe(OH)3
None of the above substances are amphoteric
The qualitative analysis procedure for separating group II cations from group II
cations begins with the following steps. Use this information to answer questions
18-19.
i. Treatment with HCl and HNO3 (aqua regia)
ii. Treatment with HNO3 and thioacetamide, CH3CSNH2
18. [7 points] What is the reason for treating with aqua regia?
a. To precipitate out remaining group I cations
b. The nitric acid is necessary to oxidize tin and antimony to their maximum
oxidation states (Sn(IV) & Sb(V))
c. The hydrochloric acid is necessary to form complex ions with Sn(IV) and
Sb(V) in order to insure that the sample completely dissolves
d. Both (b) and (c)
e. None of the above
19. [7 points] What is the role of HNO3 in the second step?
To prevent Sb2S5 and/or SnS2 precipitates from forming
To prevent formation of insoluble sulfides with group III cations
To dissolve any hydroxides that may have formed in the previous step
To provide students an additional opportunity to injure themselves with
dangerous chemicals
e. None of the above
a.
b.
c.
d.
20. [7 points] In a spontaneous process _____________?
a.
b.
c.
d.
e.
The reverse process is also spontaneous
The path between reactants and products is reversible
The path between reactants and products is irreversible
The forward and reverse processes occur at the same rate
The reverse process occurs at a higher rate than the forward process
21. [7 points] For which of the following reactions would you expect ΔSrxn to be
positive?
a. Ag+(aq) + Cl-(aq) → AgCl(s)
b. H2O(s) → H2O(g)
c. H2(g) + Cl2(g) → 2HCl(g)
d. N2(g) + 3H2(g) → 2NH3(g)
e. H2O(l) → H2O(s)
Consider the reaction:
FeO (s) + Fe (s) + O2(g) → Fe2O3(s)
And use this reaction and the following standard thermodynamic quantities as
appropriate to answer problems 22-24.
ΔHfº
(kJ/mol)
Sº
(J/mol-K)
-271.9
60.8
O2 (g)
0
205.0
Fe (s)
0
27.2
-822.2
90.0
Compound
FeO (s)
Fe2O3 (s)
22. [7 points] What is the value of ΔS for this reaction?
a.
b.
c.
d.
e.
-202.9 J/K
-1094.1 J/K
+202.9 J/K
+383.0 J/K
-383.0 J/K
23. [7 points] What is the value of ΔG0 for this reaction when it occurs under
standard conditions (pressure = 1 atm, T = 298 K). Under these conditions is it
a spontaneous reaction?
a.
b.
c.
d.
e.
-498.8 kJ, non-spontaneous
-611 kJ, spontaneous
+5.91 × 104 non-spontaneous
-498.8 kJ, spontaneous
None of the above
24. [7 points] Determine the temperature (in ºC) above which the reaction is nonspontaneous.
a.
b.
c.
d.
e.
This reaction is spontaneous at all temperatures
618.1 ºC
756.3 ºC
2439 ºC
1235 ºC
25. [7 points] The equilibrium constant for the following reaction is 5.0 × 108 at 25
ºC.
N2(g) + 3H2(g) → 2NH3(g)
The value of ΔGº for this reaction is ___________?
a.
b.
c.
d.
e.
22 kJ/mol
-4.2 kJ/mol
-25 kJ/mol
-50 kJ/mol
-22 kJ/mol