CHEM 1212 Module Eleven-Chapter 17 Name:____________
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Module Eleven:
Acid/Base Equilibria Chapter 17 |
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I. Determination of pH of polyprotic acids
and/or Buffer Calculation Problem |
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K. Determination of Kw from Kc ;
Kb from Ka & Kw ; Show Kb x Ka = Kw |
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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 çè C5H5N + H3O+1
Ka =
b. NH3 + H2O çè NH4 1+ + OH 1-
Kb =
c. H2CO3 + H2O ç=è HCO3 1- + H3O+1
Ka =
d. HCO3 1- + H2O ç==è CO3 2- + H3O+1
Ka2 =
e. C5H5N + H2O ç====è + OH 1- + C5H5N+1
Kb =
f. H2O +
H2O ç==è 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 ó H3O+1 + CH3CH2 CH2CO2-1(aq)
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CH3CH2 CH2CO2H |
H3O+1 |
CH3CH2 CH2CO2-1 |
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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:
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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)
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(b) What is the
equilibrium concentration of the sulfite ion,
SO3 2- in the 0.45 M solution of H2SO3
?
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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 à
_____2.
KNO3(s) + HOH à
_____3. NH4NO3(s) + HOH à
_____4. KC2H3O2
(s) + HOH à
_____ 5. NH4C2H3O2
(s) + HOH à
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