CHEM 1212 Module Eleven-Chapter 17 Name:____________

 

Module Eleven: Acid/Base Equilibria Chapter 17

Possible

Actual

A. Idenification of Bronsted-Lowry acids&bases

10

 

B. Writing Equilibrium Constant Expressions

10

 

C. Key Terms Chapter 17

10

 

D. Determination of pH & pOH from concentrations Problems

10

 

E. Determination of pH of weak acids/bases Problems

10

 

F. Hydrolysis Reactions 

10

 

G. Common Ion Effect Problem

10

 

H. Discussion Questions Chapter 17

5

 

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

10

 

J. Acid-Base Properties of Salts

10

 

K. Determination of Kw from Kc ; Kb from Ka & Kw ; Show Kb x Ka = Kw

10

 

M. Multiple Choice Applications -Chapter 17

10

 

Total: 115

 

Part A: Identification of Acids and Bases 10 points

Label the acid and the base and their corresponding conjugate pairs for the following reactions:

 

 

 

(1) NH4 + + Cl 1- <=====> NH3 + HCl

 

 

 

 

(2) CH3OH + C-1- <======> HCl + CH3O1-

 

 

 

 

(3) C5H5NH+1 + H2O <=======> C5H5N + H3O+1

 

 

 

 

 

(4) HSeO4 1- + NH3 <=======> NH4 1+ + SeO4 2-

 

 

 

 

 

(5) HCO3 1- + OH 1- <==========> CO3 2- + H2O

 

 

 

 

 

 

 


 

CHEM 1212 M-11 Sample Exam

Part B: Equilibrium Constant Expressions of Acids and Bases 5 points

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 =

 

 

 

Part C: Key Terms Chapter 17 10 points

Fill in the blank with word or words that best fit the description:

 

___________________1. _____is the the reaction of a substance with water.

 

___________________2. _____ are bases that have more than one hydroxide ion.

per formula unit.

___________________3. ______ may be refer to the potential of the hydrogen ion and

defined as the negative logarithm of the [H+].

___________________4. A substance that can act as either an acid or a base is said

to be ___.

___________________5. The conjugate base of water is the ___ion.

 

___________________6. The Bronsted-Lowry ____ is a proton donor.

 

___________________7. The basic ionization constant is the equilibrium constant for

a base as is represented by the symbol(s).

 

___________________8. The Bronsted-Lowry ____ is a proton acceptor.

 

___________________9. The ___ __ ____is the suppression of the ionization of a

weak acid or weak base by the presence of a common ion

from a strong electrolyte,

___________________10. A __ __ is one that changes pH only slightly when small

amounts of a strong acid or base are added.

___________________11. The critical point in a titration is called the _____ ___, the

point at which acid and base have been brought together in

stoichiometric proportions, where neither remaining in

excess.

___________________12. The point in a titration at which the indicator changes color

is known as the ___ __.

___________________13. The ionization expression for a weak acid includes the Ka

which is called the ___ ___ ___.

___________________14. The negative logarithm of the hydroxide concentration is

known as___

___________________15. Every acid has a _____ base.

 

___________________16. The negative logarithm of the Kw.

 

___________________17. __ are acids that have more than one ionizable hydrogen

atoms per molecule.

 

___________________18. Every base has a _____ acid..

 

Write the definition of any word(s) not list above which are in our Chapter 17 vocabulary list:

 

 

 

 

Part D: pH Scale Calculations 10 points

What is the pH and pOH of the following solutions:

 

 

(1) 0.000675 M HCl

 

 

 

 

 

 

 

 

(2) 0.0025 M Ca(OH)2

 

 

 

 

 

 

 

 

(3) The pH of a cup of coffee is 4.32, calculate the [H3O+1 ]:

 

 

 

 

 

 

 

 

 

 

 

(4) A detergent solution has a pH of 11.45. What is the [OH 1- ]?

 

 

 

 

 

 

 

 

 


 

 

Part E: Equilibria of Acids and Bases Calculations 10 points

Write the appropriate equilibrium constant expression for the following reaction::

 

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.

CH3CH2 CH2CO2H(aq) + H2O H3O+1 + CH3CH2 CH2CO2-1(aq)

 

 

CH3CH2 CH2CO2H

H3O+1

CH3CH2 CH2CO2-1

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Part F: Hydrolysis Calculations 10 points

What is the pH of the bleach solution which is 5.25% by weight Sodium hypochlorite?

The Ka of Hypochlorous acid is 3.5 x 10-8

 

 

 

 

 

 

 

 

 

 

Part G: Common Ion/Buffer Solution Calculations 10 points

A solution is prepared that is 1.50M HCOOH formic acid, 2.0 M Sodium formate

 

HCOOH + HOH <=====> H3O 1+ + HCOO 1-

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Part H: Discussion Questions Chapter 17 10 points

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

 

 

 

 

 

 

 

 

Write equations to show how the HCO3 1- ion can act either as an acid or a base:

 

 

 

 

 

 

 

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?

 

 

 

 

Part I: pH polyprotic acid 10 points

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

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

(Show both ionization reactions, write the equilibrium expressions for both)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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


 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Part J: pH of Salts 10 points

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

 

 

 

 

 

 

 

 

 

 

Part K: Derivation of Kw & Kb Chapter 17 10 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-

 

 

 

 

 

 

 

For Part M, Link to the many online practice multiple choice exams for chapter 17:

M.      Multiple Choice Applications -Chapter 17

http://www.hccfl.edu/faculty/john_taylor/chm1046/46mod11_12.html

http://www.brookscole.com/cgi-wadsworth/course_products_wp.pl?fid=M20bI&discipline_number=12&product_isbn_issn=003033604X