ACIDS AND BASES
OPERATIONAL DEFINITIONS
A. Classification of a substance based on
its observable properties
B. Operational definitions of acids
1. Aqueous solutions of acids conduct
electricity
a. Strong acids are good conductors of
electricity
• Therefore they must break up into many
ions
• They are strong electrolytes
• They cause the bulb of a conductivity
tester to glow brightly
b. Weak acids are poor conductors of
electricity
• Therefore they must break up into few
ions
• They are weak electrolytes
• They cause the bulb of a conductivity
tester to glow faintly
2. Acids react with metals to produce
hydrogen gas(H2)
a. Reference Table J
b. All metals found above hydrogen on
the table react with acids to produce
hydrogen gas (H2)
3. Acids cause acid-base indicators to
change color
a. indicators- substances which have
different colors in acid and base
b. examples: litmus: red in acid, blue in
base
phenolphtalein is clear in acid, pink in base
c. Table M
4. Acids react with bases (hydroxides
(OH)) to form a salt and water
a. Called a neutralization reaction
b. Example: HCl + NaOH  NaCl + HOH
c. Referred to as a titration
5. Dilute aqueous solutions of acids
have a sour taste
a. Examples: vinegar-acetic acid
Lemons- citric acid
6. Names and formulas of some common
acids are found on table K
C. Operational definitions of bases
1. aqueous solutions of bases conduct
electricity
a. Strong bases are good conductors
of electricity
• Therefore they must break up into many
ions
• They are strong electrolytes
• They cause the bulb of a conductivity
tester to glow brightly
•
b. Weak bases are poor conductors of
electricity
• Therefore they must break up into few
ions
• They are weak electrolytes
• They cause the bulb of a conductivity
tester to glow faintly
2. Bases cause acid-base indicators to
change color
a. litmus turn blue in base
b. phenolpthalien turns pink in base
c. Table M
3. Bases react with acids to form salt and
water- neutralization reaction
a. HCl + NaOH  NaCl + HOH
b. Known as a titration
4. Bases are caustic and have a slippery
or soapy feeling
5. Names and formulas of some common
bases are found on table L.
CONCEPTUAL DEFINITIONS
A. Stated in terms of inferences or
interpretations of observed facts
B. Conceptual definitions of acids and
bases
1. Theory 1: Arrhenius Theory
a. Arrhenius Acid
Substance whose water solution
contains hydrogen ions (H+) as the
only positive ions in the solution
• Sometimes instead of H+ a problem will
state that H3O+ or the hydronium ion is
present.
• ALL FORMULAS FOR ACIDS CONTAIN
AN “H” IN THE BEGINNING OF THE
COMPOUND OR A –COOH GROUP AT
THE END.
• Examples: HCl, HNO3, H2SO4, H3PO4
HCl (l) H+ (aq) + Cl- (aq)
H2SO4 (l)  2H+ (aq) + SO4 -2 (aq)
• Table K – has a list of some common
Arrhenius acids
b. Arrhenius base
• Substance whose water solution yield
hydroxide ions(OH-) as the only
negative ions in aqueous solution
• ALL BASES HAVE A METAL AND AN
(OH) IN THEIR FORMULA EXCEPT NH3
• Examples: NaOH, KOH, NH4OH
NaOH(s)  Na+ (aq) + OH- (aq)
• Table L has a list of some common
Arrenius Bases
2. Theory 2: The alternate theory of acids
and bases AKA:Bronsted-Lowry Theorya.
Alternate Theory Acid orBronsted-Lowry
Acid
1. Defined as a proton (H+) donor
Alternate Theory Base or Bronsted-Lowry
Base
2. Defined as a proton (H+) acceptor
Bronsted-Lowry Reactions
1. Each reaction contains two acid-base
pairs.
2. A pair differs only by a hydrogen,”H”
3. In the pair the species with the extra “H”
is the B-L acid the other is B-L base
Examples:
HCl + H2O H3O+ + ClNH3 (g) + H2O ↔ NH4+ (aq) + OH-(aq
AMPOHIPROTIC OR AMPHOTERIC
SUBSTANCES
A. Definition: Substances that act as
either an acid or a base depending on
the chemical environment
B. Examples:
H2O + NH3↔ NH4+ + OH–
Water donates a proton and is acting as an
acid
H2O + HNO3 ↔ H3O+ + NO3Water is accepting a proton and is acting
as a base
Other Examples HSO4- , OH-, H2PO4-,
H2O,
HPO4-2
ACID-BASE REACTIONS IN AQUEOUS
SOLUTIONS
A. Neutralization
1. A reaction in which equal molar
quantities of acid and base are mixed
2. Acid + Base  Salt + Water
• Salt is another name for an ionic
compound
• The water is formed when the H+ from the
acid combines with the OH- from the base
• What is left combines to form the salt
• Look for the word titration to indicate a
neutralization reaction.
B. Acid-Base Titrations
1. Volumetric analysis performed by
adding measured volumes of a base of
known molarity to an acid of unknown
molarity. (or vice versa)
2. The acid or base of known molarity is
called the standard solution
3. The endpoint (when neutralization is
complete) occurs when moles of H+
equals moles of OH- . It is where the
indicator changes color
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Calculating the Unknown molarity
MaVa = Mb Vb
Table T
Ma=Molarity of H+ (Usually of acid)
Va=Volume of Acid
Mb= Molarity of (OH)- (Usually of base)
Vb=Volume of base
5. Classification of acids
• Monoprotic acids have one H+ so Ma is
the same as the concentration of the acid
Ex: HCl
• Diprotic acids have two H+ so Ma is twice
the concentration of the acid
Ex: H2SO4
• Triprotic acids have three H+ so Ma is
three times the concentration of the acid
•
Ex: H3PO4
6. Examples:
a. You are titrating 62.00 ml of HCl with a
1.0M standard NaOH solution and the
following data is obtained
Initial reading: 1.00 ml
Final reading: 45.62 ml
b. 25.0 ml of .25M H2SO4 is titrated with
35.0ml of NaOH solution of unknown
concentration. Calculate the concentration
of the NaOH solution
pH
1. Def: indicates the concentration of
hydrogen ions (acid strength) in a
solution
2. pH = -log[H+]
3. pH = 7 neutral [H+] = [OH-]
4. pH < 7 acidic [H+] > [OH-]
5. pH > 7 basic [H+] < [OH-]
6. [H+][OH-] =1X10-14
What is the pH of a solution of HCl with an
[H+]of 1.0 x 10-13 M?
.pH = -log(1.0 x 10-13) hit 1.0 x 10-13 into your
calculator then hit log button then take the
negative of the answer
.pH = 13
What is the [H+] of an HCl solution with a pH
of 5?
What is the [H+] and the pH of a solution
whose [OH-] is 1 x 10-5?
7. A change of:
one pH unit represents a 10 fold change.
Two pH units represents a 100 fold change
Three pH units represents a 1000 fold
change
Four pH units represents a 1000 fold
change.
Example: If the pH decreases from 5 to 3
the substance has become 100 times
more acidic.
• If the pH increases from 7 to 9 it has
become 100 times less acidic or 100 times
more basic
How to use Table M
If the pH is below the lower limit then the solution is the first color, if the pH
is within the range the it is a mix of the two colors and if the pH is greater
than the upper limit the color of the solution if the second color listed