CHM 2046C M-11ii-Chapter 16 Homework Packet Name:_________

 

Module 11ii: Acid/Base Equilibria Jespersen Chapter 16 Homework

Possible

Actual

B. Writing Equilibrium Constant Expressions Section 16.3

1

Answer 

C. Determination of Kw from Kc ; Kb from Ka & Kw ; Show Kb x Ka = Kw Lecture/16.3

1

Answer 

E. Determination of pH of weak acids/bases Problems Section 16.5

2

Answer 

F. Hydrolysis Reactions  Section 16.6

2

Answer 

G. Common Ion Effect Problem Section 16.7

2

Answer 

H. Discussion Questions Chapter 16

1

 Answer

I. Determination of pH of polyprotic acids and/or Buffer Calculation Problem 16.8

2

Answer 

J. Acid-Base Properties of Salts Section 16.6

1

Answer 

K. Key Terms Chapter 16 p805-806 Summary

1

Answer

Module 11ii Total:

13

 

Part B: Equilibrium Constant Expressions of Acids and Bases 1 point

Write the appropriate equilibrium constant expressions for the following reactions they represent:

 

a. C5H5NH+1 + H2O C5H5N + H3O+1

 

Ka =

 

 

b. NH3 + H2O NH4 1+ + OH 1-

 

Kb =

 

 

c.                   H2CO3 + H2O = HCO3 1- + H3O+1

 

Ka =

 

 

d. HCO3 1- + H2O == CO3 2- + H3O+1

 

Ka2 =

 

 

e. C5H5N + H2O ==== + OH 1- + C5H5N+1

 

Kb =

 

 

f. H2O + H2O == H3O 1+ + OH 1-

 

Kw =

 

Reference: Jespersen Section 16.3

Try Practice 16.8; 16.9; 16.10; 16.11 Page 770;

Try Practice 16.12 and 16.13 page 771 Review Question 16.14-16.16.25 Pg 809

Answers: http://www.fccj.us/chm2046/SampleTest/46M11abAnswer.htm

 

CHM 2046C Module 11 Chapter 14 Homework Packet

Part C: Derivation of Kw Kh Kb and Ka Chapter 16 2 points

Write the ionization reaction of water, then develop the special K for water: Kw from the Kc

 

 

 

 

 

 

 

 

 

 

Write the hydrolysis reaction for Sodium acetate, NaC2H3O2 , when it is dissolved in water. Write the Kb expression for this reaction:

 

 

 

Write the ionization equilibrium expression for the Ka of acetic acid: HC2H3O2 and the Kw expression for water.

 

 

 

 

 

 

 

Derive the Kb expression from the Ka and the Kw expressions.

 

 

 

 

 

 

 

There is the following connection:

Ka x Kb = Kw

 

Using the ionization reaction of HCN in water, demonstrate the development of the above formula from the Ka of HCN and its conjugate base Kb of CN-

 

 

 

 

 

Reference: Section 16.3 Jespersen

Answers: http://www.fccj.us/chm2046/SampleTest/46M11cAnswer.htm

 

 

CHM 2046C Module 11ii Chapter 16 Homework Packet

Part E: Equilibria of Acids and Bases Calculations 2 points

Write the appropriate equilibrium constant expression for the following reaction:

 

E-1 (Determine Ka from Eq Concentrations_: A solution prepared from 0.055 mol of butanoic acid dissolved in sufficient water to give 1.0 L of solution has a pH of 2.72. Determine Ka for butanoic acid. The acid ionizes at according to the balanced equation.

CH3CH2CH2CO2H(aq) + H2O H3O+1 + CH3CH2 CH2CO2-1(aq)

 

 

CH3CH2 CH2CO2H

H3O+1

CH3CH2 CH2CO2-1

Initial

 

 

 

Change

 

 

 

Equilibrium

 

 

 

 

 

 

 

 

 

 

 

 

Reference: Section 16.4 Example 16.1 page 774; Example 16.2 Page 775
Try Practice Exercises 16.16; 16.17; 16.18 Page 776
Review Problems 16.75-16.88 Pages 811-812

 

E-2: Calculate Eq Concentrations from Ka and initial concentrations: What are the equilibrium concentrations of acetic acid, the acetate ion, and hydronium ion for a 0.10 M solution of acetic acid (Ka = 1.8 x 10-5)? What is the pH of the solution?

Ionization Reaction(you write):

 

Write the equilibrium Reactions:

 

 

 

CH3CO2H

H3O+1

CH3CO2-1

Initial

 

 

 

Change

 

 

 

Equilibrium

 

 

 

 

 

 

 

 

 

 

 

 

 

Reference: Section 16.5 Example 16.3 Page 779
Try Practice 16.22; 16.23; 16.24 Pg 780; Review Problems 16.89-16.106 p812

Answers: http://www.fccj.us/chm2046/SampleTest/46M11efAnswer.htm

Part F: Hydrolysis Calculations 2 points

E1: What is the pH of the bleach solution which is 5.25% by weight Sodium hypochlorite, NaClO?

The Ka of Hypochlorous acid is 3.5 x 10-8

 

Write Hydrolysis reactions:

 

 

 

 

ClO 1-

OH+1

HClO

Initial

 

 

 

Change

 

 

 

Equilibrium

 

 

 

 

 

 

 

 

 

 

 

E2: Calculate the pH of a 0.15M CH3NH3Cl solution. For methylamine, CH3NH2, the Kb = 4.5 x 10-4. Problem 16.102

 

Write Hydrolysis reactions:

 

 

 

 

CH3NH3 1+

H1+

CH3NH2

Initial

 

 

 

Change

 

 

 

Equilibrium

 

 

 

 

 

 

 

 

 

 

 

 

 

Reference: Section 16.6 Example 16.4 Pages 783-785

Try Practice Exercises 16.27; 16.28; 16.29; 16.30; 16.31 Page 785

Look at Review Questions 16.26-16.34 Page 809
Work Review Problems: 16.99-16.106 Page 812

Answers on Part E1 web Page:

http://www.fccj.us/chm2046/SampleTest/46M11efAnswer.htm

 

CHM 2046C Module 11ii Homework Packet

Part G: Common Ion Solution Calculations 2 points

G1.A solution is prepared that is 1.50M HCOOH formic acid and 2.0 M Sodium formate. The Ka for formic acids is: 1.8 x 10-4

 

HCOOH + HOH <=====> H3O 1+ (aq) + HCOO1- (aq)

 

HCOONa + HOH <=====> Na 1+ (aq) + HCOO1- (aq)

 

What is the pH of the formic acid before adding the Sodium formate?

 

HCOOH

H1+

HCOO1-

Initial

 

 

 

Change

 

 

 

Equilibrium

 

 

 

 

 

 

 

 

What is the pH of Sodium format solution before mixing?

 

HCOONa

OH+1

HCOOH

Initial

 

 

 

Change

 

 

 

Equilibrium

 

 

 

 

 

 

 

 

 

What is the pH of the solution of formic acid and the sodium formate if in each case the volumes of the separate solutions are the same as the volume of the mixture with the concentrations that are listed above.

 

Initial

 

 

 

Change

 

 

 

Equilibrium

 

 

 

 

 

 

 

 

 

 

 

Reference: Section 16.7 Example 16.5 Pages 787-788

Try Practice Exercises 16.34; 16.35; Page 788

Look at Review Questions 16.35-16.36 Page 809
Work Review Problems: 16.107-16.110 Page 812

Answers: http://www.fccj.us/chm2046/SampleTest/46M11gAnswer.htm

 

CHM 2046C Module 11ii Homework Packet

 

G2. Preparing a Buffer with a Desired pH:

 

How many grams of Sodium acetate must be added to 1.0L of 0.15M Acetic Acid (pKa 4.74) to make a solution a buffer with a pH of 4.00? (RP 16.117)

 

Write the ionization reactions of Acetic Acid and Sodium acetate:

 

 

 

 

 

 

Equilibrium Mixtures:

Use

 

 

Initial

 

 

 

Change

 

 

 

Equilibrium

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Reference: Section 16.7 Example 16.6 Pages 789-790

Try Practice Exercises 16.36; 16.37; Page 790

Look at Review Question 16.37 Page 810
Work Review Problems: 16.114-16.120 Page 813

 

Part H: Discussion Questions Chapter 16 1 point

Explain the difference between an Arrhenius, Bronsted-Lowry, and Lewis Acid or Arrhenius, Bronsted-Lowry, and Lewis Bases?

 

Arrhenius Acid

 

 

Bronsted-Lowry Acid

 

 

 

Lewis Acid

 

 

 

Write equations to show how the HCO3 1- ion can act either as an acid or a base (likewise for HPO4 2- , HSO4 1- or H2PO4 1-):

 

 

HCO3 1-

 

 

 

 

HPO4 2-

 

 

 

 

 

H2PO4 1-

 

 

 

 

 

 

 

HSO4 1-

 

 

 

 

 

In ionization reactions of an acid, base, or water one of the reactant molecules is water. But in the Ka, Kb, and Kw expressions, the concentration of water is not included in the calculation. Why?

 

 

 

What is the approximate molar concentration of water at room temperature?

 

 

 

 

 

 

 

 

 

Why are salts from the neutralization of a strong acid and a weak base test acidic with litmus paper (Likewise a salt from the neutralization a weak acid and strong base test basic with litmus paper)?

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Why are salts from the neutralization of a strong acid and a strong base test neutral (or a pH of 7.0) with a pH meter?

 

 

 

 

 

 

 

Answers: http://www.fccj.us/chm2046/SampleTest/46M11hAnswer.htm

 

 

CHM 2046C Module 11ii Homework Packet

Part I: pH Polyprotic acid 2 points

Sulfurous acid, H2SO3, is a weak acid capable of providing two hydrogen ions.

Ka1 = 1.2 x 10 -2 Ka2 = 6.2 x 10 -8

(a)  Show both ionization reactions,

 

 

 

(b)write the equilibrium expressions for both)

 

 

 

 

(c) What is the pH of a 0.45 M solution of H2SO3

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

(d) What is the equilibrium concentration of the sulfite ion, SO3 2- in the 0.45 M solution of H2SO3

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Reference: Section 16.8 Example 16.8 Pages 794-795

Try Practice Exercises 16.40; 16.41; Page 796

Look at Review Question 16.37 Page 810
Work Review Problems: 16.121-16.126 Page 813

Answers: http://www.fccj.us/chm2046/SampleTest/46M11iAnswer.htm

 

 

CHM 2046C Module 11ii Homework Packet

Part J: pH of Salts 1 point

Predict whether the following salts will test

A. acidic,

B. basic,

N neutral,

Not Enough Information to Predict

when dissolved in water.

 

Then show the hydrolysis reaction, if any

 

_____1. KCN(s) + HOH

 

 

 

 

_____2. KNO3(s) + HOH

 

 

 

 

_____3. NH4NO3(s) + HOH

 

 

 

 

_____4. KC2H3O2 (s) + HOH

 

 

 

 

_____ 5. NH4C2H3O2 (s) + HOH

 

 

 

 

 

Reference: Section 16.6

Reference: Section 16.6 Example 16.4 Pages 783-785

Try Practice Exercises 16.27; 16.28; 16.29; 16.30; 16.31 Page 785

Look at Review Questions 16.26-16.34 Page 809
Work Review Problems: 16.99-16.106 Page 812

 

Answers: http://www.fccj.us/chm2046/SampleTest/46M11jAnswer.htm

 

 

 

Part K: Key Terms Chapter 16 1 point

1. __________________ the equilibrium constant for the ionization of an acid in water. The general form for a generic acid HA is

 

[H3O1+][A1-]

Ka = ---------------

[HA]

 

2. __________________ the product from a Lewis acid-base reaction. In the acid-base adduct, the lone pair donated by the Lewis base is shared with an anion in the Lewis acid.

 

3. __________________ a substance that can behave either as a Bronsted acid or a Bronsted base.

 

4. __________________ a substance that can behave as either an acid or a base.

 

5. __________________ a material that produces H+ ions in aqueous solutions.

 

6. __________________ a material that produces OH ions in aqueous solutions.

 

7. __________________ a process in which molecules of the same material react with each other to produce ions. The _________ of water produced both hydronium and hydroxide ions.

 

8. __________________ the equilibrium constant for the ionization of a base in water. The general form for a generic base B is

 

[BH1+][OH1-]

Kb = ---------------

[B]

 

9. __________________ a material that can donate a proton to another substance

 

10. _________________ a material that can accept a proton from another substance

 

11. _________________ a metal ion that has Lewis bases joined to it by coordinate covalent bonds.

 

 

12. _________________ two species that differ from each other by the presence of one H + ion.

 

13. ____________________ - the attraction of electrons from adjacent bonds by an electronegative atom.

 

14. _________________ in a aqueous solution. Kw = [H3O +][OH -]

 

15. _________________ a material that accepts an electron pair in a chemical reaction

 

16. _________________ - A material that donates an electron pair in a chemical reaction

 

17. _________________ a material that is capable of donating one proton per formula unit of the acid

 

18. _________________ a material that is capable of accepting only one proton per formula unit of the acid

 

19. _________________ the negative logarithm of the hydronium ion concentration

(pH = - log [H3O+])

 

20. _________________ the negative logarithm of the hydroxide ion concentration

(pOH = - log [OH-])

 

21. _________________ a material capable of donating more than one proton per formula unit of the acid

 

22. _________________ a material capable of accepting more than one proton per formula unit of the base

 

23. _________________ - is the reaction of a substance with water

 

Reference: Chapter 16 Summary Pages 805-806