1. [7 points] The solubilty of lead (II) chloride is 1.6 ´ 10-2 M. What is the Ksp of PbCl2?
a. 5.0 ´ 10-4
b. 4.1 ´ 10-6
c. 3.1 ´ 10-7
d. 1.6 ´ 10-5
e. 1.6 ´ 10-2
2. [7 points] The Ksp for Zn(OH)2 is 5.0 ´ 10-17. Determine the molar solubility of Zn(OH)2 in buffered solution with a pH of 11.50?
a. 5.0 ´ 106
b. 1.2 ´ 10-12
c. 1.6 ´ 10-14
d. 5.0 ´ 10-12
e. 5.0 ´ 10-17
3. [7 points] For which salt should the aqueous solubility be most sensitive to pH?
a. Ca(NO3)2
b. CaF2
c. CaCl2
d. CaBr2
e. CaI2
4. [7 points] Which of the following reagents would increase the solubility of Ni(OH)2(s)?
Ni(NO3)2 NaOH HCl NH3
a. Ni(NO3)2 & NaOH
b. HCl
c. HCl & NH3
d. HCl, NaOH & NH3
e. None of these reagents will increase the solubility of Ni(OH)2
5. [7 points] The solubility of CaCO3 (limestone) is 9.5 mg in 1800 mL. What is the Ksp of CaCO3 (Formula Weight = 100.1 g/mol)?
a. 2.8 ´ 10-5
b. 2.8 ´ 10-9
c. 5.2 ´ 10-5
d. 5.2 ´ 10-9
e. 3.8 ´ 10-7
6. [7 points] What is the pH of a saturated solution of Cu(OH)2 (Ksp = 2.6 ´ 10-19)?
a. 7.9
b. 7.6
c. 6.1
d. 9.2
e. 8.8
7. [7 points] The solubility of iodide ions in a saturated solution of lead (II) iodide (Ksp = 1.4 ´ 10-8) is ______?
a. 3.8 ´ 10-4
b. 3.0 ´ 10-3
c. 1.5 ´ 10-3
d. 3.5 ´ 10-9
e. 1.4 ´ 10-8
8. [7 points] In which one of the following solutions is silver chloride the most soluble?
a. 0.181 M HCl solution
b. 0.0176 M NH3 solution
c. Pure water
d. 0.744 M LiNO3 solution
e. 0.181 M NaCl solution
9. [7 points] A solution contains three anions with the following concentrations, 0.20 M CrO42-, 0.10 M CO32- and 0.01 M Cl-. If a dilute AgNO3 solution is slowly added to the solution what is the first precipitate to form: Ag2CrO4 (Ksp = 1.2 ´ 10-12), Ag2CO3 (Ksp = 8.1 ´ 10-12), AgCl (Ksp = 1.8 ´ 10-10)?
a. Ag2CrO4
b. Ag2CO3
c. AgCl
d. No precipitates will form
10. [7 points] The Ksp for BaF2 is 1.0 ´ 10-6. When 10 mL of 0.010 M NaF is mixed with 10 mL of 0.01 M BaNO3 will a precipitate form?
a. No, because Q = 1.0 ´ 10-4 and since it is larger than Ksp no precipitate will form
b. Yes, because Q = 1.0 ´ 10-4 and since it is larger than Ksp a precipitate will form
c. No, because Q = 1.3 ´ 10-7 and since it is less than Ksp no precipitate will form
d. Yes, because Q = 1.3 ´ 10-7 and since it is less than Ksp a precipitate will form
e. Not enough information is given to answer this question
The qualitative analysis procedure for Group III cations (Al3+, Fe3+, Cr3+, Ni2+, Co2+, Zn2+) begins with the following three steps. Use this information to answer questions 11-12.
i. Treatment with HCl and H2O2
ii. Evaporation to a paste, followed by addition of dilute HCl
iii. Treatment with a solution containing NH4Cl and NH3
11. [7 points] What is the main purpose of the hydrogen peroxide in the first step?
a. To prevent formation of complex ions with chloride
b. To oxidize Cr3+ to Cr6+
c. To oxidize Co2+ to Co3+
d. To insure all of the iron is present as Fe3+
e. None of the above
12. [7 points] How will the separation be affected if the ammonium chloride is omitted and excess ammonia is added in the third step?
a. Ni(OH)2 precipitate will form and the Ni2+ ions will end up in the aluminum subgroup
b. Fe(NH3)63+ complex ions will form and the Fe3+ ions will end up in the nickel subgroup
c. Al(NH3)63+ complex ions will form and the Al3+ ions will end up in the nickel subgroup
d. Al(OH)4- complex ions will form and the Al3+ ions will end up in the nickel subgroup
e. The Cr3+ ions will be oxidized to form CrO42- ions
13. [7 points] What color is Ni(NH3)62+(aq)?
a. blue
b. red
c. orange
d. yellow
e. pink
14. [7 points] A solution contains three of the following cations: Sn4+, Sb5+, Co2+, Fe3+, Cr3+, Bi3+ and Ag+. When HCl was added and the test tube was chilled, a white precipitate (ppt A) formed. The supernatant liquid (sol’n B) was decanted from the precipitate. HNO3 and thioacetamide (CH3CSNH2) were added to sol’n B and the solution was heated. This led to the formation of a yellow precipitate (ppt C). The supernatant liquid (sol’n D) was decanted from the precipitate, and the solution was evaporated to a paste. The residue was dissolved in dilute HCl. Finally NH4Cl and NH3 were added and a pink solution was formed in the but no precipitate. Which three cations must be present?
a. Ag+, Co2+ & Sb4+
b. Cr3+, Co2+ & Sn4+
c. Bi3+, Co2+ & Fe3+
d. Ag+, Cr3+ & Sn4+
e. Ag+, Co2+ & Sn4+
15. [7 points] A solution may contain any or all of the following ions: Cu2+, Ni2+, Pb2+, Al3+ and Sn4+. The acidity of the solution was adjusted to a pH = 0.4 with HNO3 and thioacetamide (CH3CSNH2) was added. Heating produced a black precipitate (ppt A), and a green solution (sol’n B). Ppt A didn’t dissolve in 3 M NaOH but it did dissolve in 6 M HNO3 producing a colorless solution. Sol’n B was evaporated to a paste and dissolved in dilute HCl. Finally NH4Cl and NH3 were added and a blue solution was formed but no precipitate. Which cations must be present?
a. Pb2+ and Al3+
b. Cu2+, Ni2+ and Sn4+
c. Pb2+, Ni2+ and Al3+
d. Pb2+ and Ni2+
e. Pb2+, Ni2+ and Sn4+
16. [7 points] What reagent could be used to separate Pb2+ and Bi3+?
a. H2SO4
b. HNO3
c. Thioacetamide, CH3CSNH2 and heat
d. NH3
e. NaOH
17. [7 points] What happens when Bi(OH)3 is brought in contact with Sn(OH)3- ions?
a. A Sn(OH)2 precipitate forms
b. Tin is reduced to metallic tin, Sn, and bismuth is oxidized to Bi5+
c. Tin is oxidized to Sn4+, and bismuth is reduced to metallic bismuth, Bi
d. The Bi(OH)3 dissolves due to the common ion effect
e. There is no reaction between these two substances
18. [7 points] The formation constant, Kf, for Ni(NH3)62+ is 5.5 ´ 108. What is the concentration of free nickel ions in a solution that contains 0.045 M Ni2+ and 3.0 M NH3 (concentrations refer to the moment before the formation of the complex ion)?
a. 0.045 M
b. 3.0 ´ 10-11 M
c. 1.1 ´ 10-7 M
d. 2.95
e. None of the above
19. [7 points] The entropy of the universe is ______?
a. constant
b. continually decreasing
c. continually increasing
d. zero
e. the same as the energy, E
20. [7 points] For which of the following reactions would you expect DSrxn to be positive?
a. 2H2(g) + O2(g) ® 2H2O(g)
b. 2NO2(g) ® N2O4(g)
c. CO2(g) ® CO2(s)
d. 2Hg(l) + O2(g) ® 2HgO (s)
e. None of the above reactions will have a positive DS
21. [7 points] The combustion of butane can be expressed with the following reaction:
2 C4H10(g) + 13 O2(g) ® 8 CO2(g) + 10 H2O(g)
What sign would you expect for the enthalpy, entropy and Gibbs free energy?
a. DS < 0 (negative), DH < 0 (negative), DG < 0 (negative)
b. DS > 0 (positive), DH < 0 (negative), DG < 0 (negative)
c. DS > 0 (positive), DH > 0 (positive), DG > 0 (positive)
d. DS < 0 (negative), DH > 0 (positive), DG > 0 (positive)
e. DS > 0 (positive), DH < 0 (negative), but the sign of DG is hard to know for sure and may change with temperature
Consider the combustion of ethene:
C2H4 (g) + 3O2 (g) ® 2CO2(g) + 2H2O(l)
And use this reaction and the following standard thermodynamic quantities as appropriate to answer problems 22-24.
Compound / DHfº (kJ/mol) / DGfº (kJ/mol) / Sº (J/mol-K)C2H4 (g) / 52.3 / 68.1 / 219.4
O2 (g) / 0 / 0 / 205.0
CO2 (g) / -393.5 / -394.4 / 213.6
H2O (l) / -285.8 / -237.1 / 69.9
22. [7 points] What is the value of DS for the combustion of ethene?
a. -267.4 J/K
b. -140.9 J/K
c. -347.6 J/K
d. +347.6 J/K
e. +140.9 J/K
23. [7 points] What is the value of DG0 for the combustion of ethene under standard conditions (pressure = 1 atm, T = 298 K)?
a. -699.6 kJ
b. -1263 kJ
c. -1124 kJ
d. -1331 kJ
e. None of the above
24. [7 points] What is the value of DG0 for the combustion of ethene at 800 ºC?
a. -699.6 kJ
b. -1197 kJ
c. -1124 kJ
d. -1331 kJ
e. None of the above
25. [7 points] With thermodynamics one cannot determine ______?
a. the value of the equilibrium constant
b. the speed of a reaction
c. the direction of a spontaneous reactions
d. the extent of a reaction
e. the temperature at which a reaction will be spontaneous