Northrup's Chem 112 Section TTU General Chemistry

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Chem 112 - Quiz 6B - Spring, 1998
Chapters 19 and 20: Ionic Equilibria II, Hydrolysis and Titrations

1. The Ksp of bismuth iodide, BiI3, is 8.1 x 10-19. How many grams of this compound can dissolve in a Liter of aqueous solution?

BiI3(s) <---> Bi3+ + 3 I-
a) 4.8 x 10-16 g
b) 8.1 x 10-19 g
c) 1.3 x 10-5 g
d) 3.0 x 10-20 g
e) 7.8 x 10-3 g

2. Which is an INCORRECT match?

a) Ca3(PO4) = bones and teeth
b) CaCO3 = limestone
c) BaSO4 = x-ray imaging
d) all are correct matches

3. The mineral sphalerite found in zinc mines near Lebanon, Tennessee is composed of ZnS. The molar solubility of ZnS in water is 3.3 x 10-11 moles/L. What is the Ksp of ZnS?

a) 2.14 x 10-4
b) 1.1 x 10-21
c) 5.7 x 10-6
d) 3.3 x 10-11

4. Nickel carbonate, NiCO3, has a Ksp of 6.6 x 10-9. What is the molar solubility of nickel carbonate?

a) 3.9 x 10-3 mol/L
b)4.35 x 10-17 mol/L
c) 6.6 x 10-9 mol/L
d) 8.1 x 10-5 mol/L

5. A 1.000 L solution is prepared in which Ni2+, Ag+, and Mn2+ ions are present in solution, all at a concentration of 0.0010 M. A solution of sodium sulfide Na2S is slowly added. Which compound will begin to precipitate FIRST? The Ksp of NiS = 3.0 x 10-21; Ag2S = 1.0 x 10-49; MnS = 5.1 x 10-15.

a) Ag2S
b) NiS
c) MnS
d) Na2S

6. In Problem #5, at what concentration [S2-] will precipitation of the first salt begin?

a) 0.001 M
b) 3.0 x 10-18 M
c) 5.1 x 10-12 M
d) 1.0 x 10-43 M

7. Which of the following is the INCORRECT statement?

a) Reduction results in a decrease in oxidation number.
b) The oxidation number of oxygen atoms in ozone, O3, is zero.
c) Reduction is a loss of electrons.
d) The oxidizing agent in a redox reaction is reduced.
e) Electrons are being transferred in a redox reaction.

8. Which substance is being oxidized in the following reaction?

Zn(s) + 4 CN-(aq) + Ag2CrO4(s) ----> Zn(CN) 42- + 2 Ag(s) + CrO42-(aq)

a) CN-(aq) ions
b) Ag(s)
c) Zn(s)
d) Ag+(aq) ions
e) H2(g)

9. What is the oxidation number of Cl in HClO2?

a) -1
b) +2
c) +4
d) +5
e) +3

Questions 10-11:

Given the following incomplete redox reaction, balance this equation in ACID solution with the set of smallest whole number coefficients:

MnO2 + Cl-(aq) ---> Mn2+(aq) + Cl2(g)

10. Identify the CORRECT statement below:

a) MnO2 and Cl-(aq) react in a 5 to 2 mole ratio, respectively.
b) MnO2 and Cl-(aq) react in a 1 to 2 mole ratio, respectively.
c) MnO2 and Cl-(aq) react in a 5 to 1 mole ratio, respectively.
d) no H2O or H+ needed.

11. To balance this redox equation requires:

a) 4 OH- on the left and 4 H+ on the right.
b) 4 H+ on the left and 4 H2O on the right.
c) 8 H+ on the left and 4 H2O on the right.
d) 4 H2O on the left and 2 H+ on the right.
e) 4 H+ on the left and 2 H2O on the right.

12. Identify the INCORRECT statement in the following:

a) One Faraday of charge will reduce exactly one mole of Zn2+ ions to Zn(s).
b) In an electrolytic cell a nonspontaneous reaction is made to take place by applying an external electric current.
c) The cathode is the site of reduction in an electrochemical cell.
d) Measuring the potential of a cell provides a direct determination of the free energy of the cell reaction.
e) Sodium metal and chlorine gas are produced in an electrolytic cell containing pure molten NaCl.

13. How many grams of Ag(s) could be plated out on the cathode of an electrolytic cell by the passage of 5.0 Amps of current through AgNO3 solution for 1 hour? Faraday's number = 96485 Coul/mol.

a) 5.5 x 10-3 g
b) 0.19 g
c) 5.2 x 10-5 g
d) 20 g

14. Copper can exist in solution as Cu+ or Cu2+. Suppose a 1.00 Amp current applied for 30.0 minutes produced 1.185 grams of Cu(s). What oxidation state is the copper in solution?

a) +2
b) +1
c) 0
d) cannot tell

15. Referring to the table of Standard Cell Potentials below, determine the standard cell potential for the following reaction:

Pb2+(aq) + 2 Cl-(aq) ---> Pb(s) + Cl2 
                                     E°

Pb2+(aq)  +  2e-  --->  Pb(s)      -0.126
Cl2  +  2e-  ---> 2 Cl-(aq)         +1.360

a) +1.486
b) -1.486
c) +1.234
d) -1.234

16. Which metal is most easily oxidized to its cationic form?

a) Ag
b) Cu
c) Na
d) Pb

17. In the Daniell cell the overall reaction is:

Zn(s) + Cu2+(aq) ---> Zn2+(aq) + Cu(s)

Which of the following reactions is taking place at the cathode?

a) Cu2+(aq) + 2e- ---> Cu(s)
b) Zn(s) ---> Zn2+(aq) + 2e-
c) Cu(s) ---> Cu2+(aq) + 2e-
d) Zn2+(aq) + 2e- ---> Zn(s)

KEY

1)e 2)d 3)b 4)d 5)a 6)d 7)c 8)c 9)e 10)b 11)e 12)a 13)d 14)b 15)b 16)c 17)a
To send electronic mail to Dr. Northrup ====> snorthrup@tntech.edu, or call 615-372-3421, or come to Foster Hall 219