Northrup's Chem 112 Section TTU General Chemistry

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Chem 112 - Quiz 6A - Spring, 1997
Chapters 19 and 20: Ionic Equilibria II, Hydrolysis and Titrations

1. Which salt dissolved in water will give the highest pH?

a) NaCl
b) KBr
c) NaNO3
d) NH4Cl
e) NaF

2. The Ka of the weak acid HNO2 is 7.4 x 10-4. What is the Kb of its conjugate base, NO2-?

a) 7.4 x 10-4
b) 1.35 x 103
c) 1.35 x 10-11
d) 1.0 x 10-14
e) 1.8 x 10-5

3. What is the pH of 0.10 M sodium acetate (NaAc) solution? The Ka of acetic acid (HAc) is 1.8 x 10-5.

a) 1.0
b) 0.10
c) 7.0
d) 8.9
e) 5.1

4. Which titration curve below represents the titration of a strong base with a strong acid titrant?

Consider the following table of indicator ranges.

5. Which indicator(s) would be the best choice for the titration like the (b) curve in Problem #4?

a) Methyl orange and methyl red would work best.
b) Bromothymol blue and phenolphthalein would work.
c) Methyl red would be best.
d) Phenolphthalein would work best.

6. The Ksp of Bi2S3 is 1.6 x 10-72. What is the molar solubility of this compound in aqueous solution?

a) 1.6 x 10-72 M
b) 4.4 x 10-15 M
c) 1.7 x 10-15 M
d) 1.2 x 10-24 M

7. Which is an INCORRECT match?

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

8. The mineral fluorite is composed of CaF2. The molar solubility of calcium fluoride in water is 2.1 x 10-4 moles/L. What is the Ksp of CaF2?

a) 3.7 x 10-11
b) 2.14 x 10-4
c) 4.6 x 10-8
d) 9.8 x 10-12

9. Gold chloride, AuCl, has a Ksp of 2.0 x 10-13. How many grams of gold are found in 500 mL of a saturated aqueous solution of AuCl?

a) 1.0 x 10-13 g
b) 4.5 x 10-7 g
c) 2.2 x 10-7 g
d) 4.4 x 10-5 g

10. A 1.000 L solution is prepared in which Au+, Ag+, and Cu+ ions are present in solution as nitrates, all at a concentration of 0.0010 M. A solution of sodium chloride is slowly added. Which compound will begin to precipitate first? The Ksp of AuCl = 2.0 x 10-13; AgCl = 1.8 x 10-10; CuCl = 1.9 x 10-7.

a) CuCl
b) AgCl
c) AuCl
d) NaNO3
e) NaCl

11. In Problem #10, at what concentration [Cl-] will precipitation of the first salt begin?

a) 2.0 x 10-13 M
b) 2.0 x 10-10 M
c) 4.5 x 10-7 M
d) 1.9 x 10-4 M

12. Which of the following is the INCORRECT statement?

a) The oxidation number of chlorine atoms in Cl2 is zero.
b) Oxidation results in an increase in oxidation number.
c) The oxidizing agent in a redox reaction is reduced.
d) Electrons are being transferred in a redox reaction.
e) Reduction is a loss of electrons.

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

2 HCl(aq) + Zn(s) --> ZnCl2(aq) + H2(g)
a) H+(aq) ions
b) Cl-(aq) ions
c) Zn(s)
d) Zn2+(aq) ions
e) H2(g)

14. What is the oxidation number of Cr in K2Cr2O7?

a) +2
b) +3
c) +7
d) +6
e) +5

Questions 15-16:

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

Zn(s) + NO3-(aq) --> Zn2+(aq) + N2(g)

15. Identify the CORRECT statement below:

a) Zn(s) and NO3- react in a 1 to 2 mole ratio, respectively.
b) Zn(s) and NO3- react in a 5 to 2 mole ratio, respectively.
c) Zn(s) and NO3- react in a 2 to 5 mole ratio, respectively.
d) Zn(s) and NO3- react in a 5 to 1 mole ratio, respectively.

16. To balance this redox equation requires:

a) 6 H+ on the left and 6 H2O on the right.
b) 6 H+ on the left and 3 H2O on the right.
c) 12 H+ on the left and 6 H2O on the right.
d) 6 H2O on the left and 6 H+ on the right.
e) 6 OH- on the left and 6 H+ on the right.

KEY

1)e 2)c 3)d 4)a 5)d 6)c 7)d 8)a 9)d 10)c 11)b 12)e 13)c 14)d 15)b 16)c
To send electronic mail to Dr. Northrup ====> snorthrup@tntech.edu, or call 615-372-3421, or come to Foster Hall 333