Definitions and Concepts:
Arrhenius Defn:
Acid :
Base :
The Arrhenius definition is useful only in a _____________
solution (solvent).
Bronsted-Lowry Defn:
Acid :
Base :
The B-L definition envisions acid/base reactions as
a competition for __________.
Lewis Defn:
Acid :
Base :
When a Lewis acid and a Lewis base react a ______________ ______________ bond is formed.
Names and formulas of SIX common Strong Acids:
Names and formulas of SIX common Strong Bases:
The Bronsted Lowry definition of acids & bases
introduces the concept of "Conjugate Acid/Base pairs" Give four examples
of conjugate pairs including two in which water is conjugate acid and and
the other conjugate base:
Explain briefly why a strong Bronsted Acid has a very
weak conjugate base. Give an example.
Explain briefly why a weak Bronsted Acid has a much
stronger conjugate base. Give an example.
Acid strength is related to molecular structure:
What two factors make a hydrogen containing compound more or less acidic.
Explain the order of acidities in terms of the above concepts:
Oxo-acid strengths, unlike the above, are fairly predictable
on the basis of electronegativity, explain:
Explain the order of acidities in this series of oxo-acids in terms of conjugate base strength:
Polyprotic acids have more than one ____________ per molecule to donate.
The acidity of the second ionization is always ___________ than that of the first.
Explain using H3PO4
Actually PO4(3-)
is a quite strong base. Explain:
Write the equation for the autoionization of water
and write the equilibrium expression Kc.
Explain how Kw is obtained. What is its value,
and at what temperature?
Why is Kw not constant with temperature. Will
Kw increase or decrease with temperature increase, explain using LeChatelier's
Principle.
At a given temperature does one always know the [OH-] if the [H+] is known?
__________. Why (or why not?)
What are the concentrations of hydrogen and hydroxide ions in pure water at 25 C?
In 1.0 M HCl:
In 1.0 M NaOH
Write the definitions of pH, pOH, pKw, pKa, pKb:
How is the relationship: pH + pOH
= pKw related to [H+][OH-] = Kw
Write the abbreviated general formula for the dissociation
of a Weak Acid and the Ka expression.
Write the abbreviated general formula for the dissociation
of a Weak Base and the Kb expression.
Why can the assumption that [HA]equil
= [HA]init
for a dilute aqueous solution of a weak acid commonly be made. What
are its limitations?
Define the percent ionization for a weak acid.
Why does it always get larger the more dilute the acid is made. What
principle is involved?
When a weak acid HA dissociates in water why is the
[H+] = [A-]?
When the pH of a polyprotic acid is calculated, why
is only the first ionization usually considered?
Given that a 0.0015 M solution of quinine has a pH
= 9.84, calculate Kb.
Explain why some acid-base salts form neutral aqueous
solutions and others are acidic or basic. Explain why this occurs
and write equations of an acidic and a basic salt.
If one knows the Ka of a bronsted acid why do we also
know the Kb of its conjugate base. What is the mathematical relationship?
Calculate the pH of a 0.10 M ammonium chloride solution:
Calculate the pH of a 0.10 M sodium cyanide solution:
calculate the pH of a 0.10 M sodium chloride solution:
The "common ion effect" is another example of LeChatelier's
Principle. Explain what happens to 100.0 mL a 0.10 molar solution
of acetic acid as solid sodium acetate is gradually added.
What will the pH of this acid be in pure water:
What will the pH of this acid be if the sodium acetate
concentration becomes equal to the acetic acid concentration.
What property of the just mentioned solution makes
it resist changes in pH? Explain what will happen using chemical
equations if 1) a small quantity of strong acid or 2) strong base is added.
All buffers have a pair of conjugate acids and bases
in concentration ratios that vary between what values thus limiting the
pH to pKa plus-minus a half pH unit.
What is the ideal conjugate ratio for a buffer, what
will be its pH?
When one challenges a buffer with a small quantity
of acid or base, stoichiometry is used to calculate the conjugate ratio
of the resulting solution. Write the equation which relates pH to
pKa and the conjugate ratio. What is the name of this equation.
Base buffers work the same way as acid buffers:
What is the conjugate ratio of a basic buffer whose pOH = pKb?
Can you see how to use the general buffer equation
for both an acid and a base derived buffer? What value do you
need besides the conjugate ratio to calculate the pH directly for a base
buffer?
Titration of an acid with a base or vice versa is a
useful laboratory procedure for determining the concentration of an unknown
acid or base. In this procedure a known volume of the unknown is
titrated with a known concentration of the standard and the volume required
measured with a ___________ and the end-point is detected by means of an
acid-base _________________ which changes color. Write the equation
for a titration at the end-point:
When one titrates a strong acid with a strong base the end point will occur when the pH = ___________
The end-point of the titration of a weak acid with
a strong base will occur at a pH which indicates a slightly ___________
solution. Explain this observation.
The end-point of the titration of a weak base with
a strong acid will occur at a pH which indicates a slightly ___________
solution. Explain this observation.
When either of the above titrations is half-way to
the endpoint the pH will change very sluggishly (resists changing).
Why is this occurring?
What is the pH of a solution halfway to the end-point?
What property makes a compound a good acid-base indicator?