Top Banner
Page 1 of 13 Exam 2 Practice - Answers Chem 163 - K. Marr Contents: Chemical Equilibrium Practice Problems (Sets 1 & Set 2) and a Practice Test Acid - Base Equilibria Practice Problems and a Practice Test Precipitation Reactions (K sp ) Practice Problems Chemical Equilibrium Practice Set 1
13

Exam 2 Practice - Green River Collegeinstruction.greenriver.edu/kmarr/Chem 163/Exam Study Guides/Chem... · Exam 2 Practice - Answers ... PR A C TI C E PR OB L EM S Sorry—I can’t

Mar 06, 2018

Download

Documents

buinhi
Welcome message from author
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Page 1: Exam 2 Practice - Green River Collegeinstruction.greenriver.edu/kmarr/Chem 163/Exam Study Guides/Chem... · Exam 2 Practice - Answers ... PR A C TI C E PR OB L EM S Sorry—I can’t

Page 1 of 13

Exam 2 Practice - Answers

Chem 163 - K. Marr

Contents:

Chemical Equilibrium Practice Problems (Sets 1 & Set 2) and a Practice Test

Acid - Base Equilibria Practice Problems and a Practice Test

Precipitation Reactions (Ksp) Practice Problems

Chemical Equilibrium – Practice Set 1

Page 2: Exam 2 Practice - Green River Collegeinstruction.greenriver.edu/kmarr/Chem 163/Exam Study Guides/Chem... · Exam 2 Practice - Answers ... PR A C TI C E PR OB L EM S Sorry—I can’t

Page 2 of 13

Page 3: Exam 2 Practice - Green River Collegeinstruction.greenriver.edu/kmarr/Chem 163/Exam Study Guides/Chem... · Exam 2 Practice - Answers ... PR A C TI C E PR OB L EM S Sorry—I can’t

Page 3 of 13

Chemical Equilibrium – Practice Set 2

Page 4: Exam 2 Practice - Green River Collegeinstruction.greenriver.edu/kmarr/Chem 163/Exam Study Guides/Chem... · Exam 2 Practice - Answers ... PR A C TI C E PR OB L EM S Sorry—I can’t

Page 4 of 13

Page 5: Exam 2 Practice - Green River Collegeinstruction.greenriver.edu/kmarr/Chem 163/Exam Study Guides/Chem... · Exam 2 Practice - Answers ... PR A C TI C E PR OB L EM S Sorry—I can’t

Page 5 of 13

Chemical Equilibrium – Practice Test

Page 6: Exam 2 Practice - Green River Collegeinstruction.greenriver.edu/kmarr/Chem 163/Exam Study Guides/Chem... · Exam 2 Practice - Answers ... PR A C TI C E PR OB L EM S Sorry—I can’t

Page 6 of 13

Page 7: Exam 2 Practice - Green River Collegeinstruction.greenriver.edu/kmarr/Chem 163/Exam Study Guides/Chem... · Exam 2 Practice - Answers ... PR A C TI C E PR OB L EM S Sorry—I can’t

Page 7 of 13

Acid - Base Equilibria

P R A C T I C E P R O B L E M S

Sorry—I can’t find the answer key to this one!

1. For the following aqueous equilibria, designate the Brønsted-Lowry conjugate acid-base pairs and

establish the weaker side:

a. NH3(aq) + H2O(l) NH4+(aq) + OH

(aq)

b. HCN(aq) + H2O(l) H3O+(aq) + CN

(aq)

c. NH4+(aq) + CO3

2(aq) NH3(aq) + HCO3

(aq)

2. Write the formula for the conjugate bases of the following:

a. HNO2

b. H2SO4

c. H2PO4

d. HF

e. CH3CO2H

3. Complete the Brønsted-Lowry equilibria, label the components acid or base, and pair up the conjugate

acid-base pairs:

a. HSO4 + H2O

b. NH3 + H2O

c. CN + H2O

d. H + H2O

e. HClO4 + H2O

4. Is the monohydrogenphosphate ion HPO42-

amphiprotic?

If so, write the formulas of its conjugate acid and its conjugate base.

5. Of the following acids, determine

a. The strongest acid

b. The acid that produces the lowest concentration of hydronium ions per mole of acid

c. The acid with the strongest conjugate base

d. The diprotic acid

e. The strong acid

f. The acid with the weakest conjugate base

HNO3(aq) + H2O(l) H3O+(aq) + NO3

(aq) Ka = very large

HSO4(aq) + H2O(l) H3O

+(aq) + SO4

(aq) Ka = 1.2 x 10

2

HCN(aq) + H2O(l) H3O+(aq) + CN

(aq) Ka = 4.0 x 10

10

H2CO3(aq) + H2O(l) H3O+(aq) + HCO3

(aq) Ka = 4.2 x 10

7

NH4+(aq) + H2O(l) H3O

+(aq) + NH3(aq) Ka = 5.6 x 10

10

HF(aq) + H2O(l) H3O+(aq) + F

(aq) Ka = 7.2 x 10

4

Page 8: Exam 2 Practice - Green River Collegeinstruction.greenriver.edu/kmarr/Chem 163/Exam Study Guides/Chem... · Exam 2 Practice - Answers ... PR A C TI C E PR OB L EM S Sorry—I can’t

Page 8 of 13

6. Write net ionic acid-base reactions for:

a. The reaction of acetic acid with aqueous ammonia solution

b. The reaction of hydrofluoric acid with sodium hydroxide

c. The reaction of ammonium chloride with potassium hydroxide

d. The reaction of sodium bicarbonate with sulfuric acid

e. The reaction of chlorous acid with aqueous ammonia solution

f. The reaction of disodium hydrogen phosphate with acetic acid

7. What is the pH of

a. 0.0010 M HCl solution?

b. 0.15 M KOH solution?

c. 10-8

M HNO3 solution?

8. List the following substances in order of increasing acid strength: (Look up the Ka’s in the appendix of

your textbook)

H2O, H2SO3, HCN, H2PO4, NH4

+, [Cu(H2O)6]

2+, NH3, H3O

+, HCO2H, HCl.

9. Complete the table for each aqueous solution at 25°C.

State whether the solutions are acidic or basic.

[H3O+] [OH

] pH pOH acidic or basic

2.0 x 105

6.25

5.6 x 102

9.20

8.7 x 1010

10. What is the pH of a solution that contains 2.60 grams of NaOH in 250 mL of aqueous solution?

11. If the pH of a sample of rainwater is 4.62, what is the hydronium ion concentration [H3O+] and the

hydroxide ion concentration [OH] in the rainwater?

12. A 0.12 M solution of an unknown weak acid has a pH of 4.26 at 25°C. What is the hydronium ion

concentration in the solution and what is the value of its Ka?

13. Hydroxylamine is a weak base with a Kb = 6.6 x 109

. What is the pH of a 0.36 M solution of

hydroxylamine in water at 25°C?

14. Suppose you dissolved benzoic acid in water to make a 0.15 M solution. Ka for benzoic acid = 6.3 x 10-5

at

25°C. What is:

a. the concentration of benzoic acid?

b. the concentration of hydronium ion?

c. the concentration of benzoate anion?

d. the pH of the solution?

Page 9: Exam 2 Practice - Green River Collegeinstruction.greenriver.edu/kmarr/Chem 163/Exam Study Guides/Chem... · Exam 2 Practice - Answers ... PR A C TI C E PR OB L EM S Sorry—I can’t

Page 9 of 13

15. Which of the following salts, when dissolved in water to produce 0.10 M solutions, would have the lowest

pH?

a. sodium acetate d. magnesium nitrate

b. potassium chloride e. potassium cyanide

c. sodium bisulfate

16. For each of the following salts, predict whether an aqueous solution would be acidic, basic, or neutral.

a. sodium nitrate NaNO3

b. ammonium iodide NH4I

c. sodium bicarbonate NaHCO3

d. ammonium cyanide NH4CN

e. sodium hypochlorite NaOCl

f. potassium acetate KCH3CO2

17. a. Cyanic acid HOCN has a Ka = 3.5 x 104

, what is the Kb for the cyanate ion OCN

b. Phenol is a relatively weak acid, Ka = 1.3 x 1010

. How does the strength of its conjugate base

compare with the strength of ammonia, the acetate ion, and sodium hydroxide?

18. a. What is the pH of a 0.80 M solution of sulfurous acid?

b. What is the concentration of sulfite ion in a 0.80 M solution of sulfurous acid?

c. What happens to the concentration of sulfite ion SO32

if the concentration of sulfurous acid

is halved?

19. Identify the Lewis acid and the Lewis base in the following reactions:

a. Boron trichloride reacts with chloride ion to produce [BCl 4]

b. Nickel reacts with carbon monoxide to produce nickel tetracarbonyl [Ni(CO)4].

c. Ammonia reacts with acetic acid to produce ammonium acetate.

d. Sodium ions are solvated by water to produce Na+(aq)

20. Calculate the pH of a 0.35 M solution of potassium cyanide. Ka for HCN = 4.0 x1010

.

Note: Question #20.

In the answers, the authors forgot to change the Ka into the Kb.

The Kb should be 2.5 x 10-5

. The "x" = [OH-] = .002958; pOH = 2.53; pH = 11.47

Page 10: Exam 2 Practice - Green River Collegeinstruction.greenriver.edu/kmarr/Chem 163/Exam Study Guides/Chem... · Exam 2 Practice - Answers ... PR A C TI C E PR OB L EM S Sorry—I can’t

Page 10 of 13

Acid – Base Reactions – Practice Test

Page 11: Exam 2 Practice - Green River Collegeinstruction.greenriver.edu/kmarr/Chem 163/Exam Study Guides/Chem... · Exam 2 Practice - Answers ... PR A C TI C E PR OB L EM S Sorry—I can’t

Page 11 of 13

Page 12: Exam 2 Practice - Green River Collegeinstruction.greenriver.edu/kmarr/Chem 163/Exam Study Guides/Chem... · Exam 2 Practice - Answers ... PR A C TI C E PR OB L EM S Sorry—I can’t

Page 12 of 13

Precipitation Reactions

P r a c t i c e P r o b l e m s

4. The solubility of lead (II) carbonate is 2.7 x 10¯7 mol L¯

1. What is its Ksp?

(A) 5.2 x 10¯4

(B) 2.7 x 10¯7

(C) 7.3 x 10¯14

(D) 3.9 x 10¯20

5. The solubility of PbI2 is 0.0013 mol L¯1. Use this information to find the Ksp for PbI2.

(A) 1.7 x 10¯6

(B) 6.8 x 10¯6

(C) 2.2 x 10¯9 (D) 8.8 x 10¯

9

6. The Ksp of CuCl is 1.9 x 10¯7 at 25 °C. What is the solubility of CuCl in mol L¯

1?

(A) 3.6 x 10¯14

(B) 1.9 x 10¯7

(C) 4.4 x 10¯4 (D) 8.8 x 10¯

4

7. The Ksp of PbI2(s) is 1.4 x 10¯8 at 25 °C. What is the solubility of PbI2 in moles per liter?

(A) 1.2 x 10¯4

(B) 1.5 x 10¯3

(C) 1.9 x 10¯3

(D) 2.4 x 10¯3

Page 13: Exam 2 Practice - Green River Collegeinstruction.greenriver.edu/kmarr/Chem 163/Exam Study Guides/Chem... · Exam 2 Practice - Answers ... PR A C TI C E PR OB L EM S Sorry—I can’t

Page 13 of 13