Acids & Bases
Properties of Acids

Taste SOUR (ex: lemons, vinegar)
Corrosive to Metals

Produces H+ ions



Which is the same as H3O+ (hydronium ion)
Proton (H+) Donor

Example: HCl + H2O  Cl- + H3O+
Strong Acid vs Weak Acid
Strong Acid – an acid that completely dissociates to
produce H+ ions in solution (lot of H+)

HCl, HNO3
Weak Acid – an acid that dissociates to a slight extent
in aqueous solution (not that many H+)

HC2H3O2 (vinegar), lemon juice
Strong Acids vs. Weak Acids
Indicators

An indicator is a chemical that will change colors when
placed in an acidic, basic or neutral environment
Indicator Colors for Acids
Litmus paper = red
Phenolphthalein = clear
Methyl orange = red
Properties of Bases

Tastes Bitter (banana peel, dark chocolate, parsley)

Feels slippery (soap)

Produces OH- ions
Proton (H+) Acceptor


Example: NH3 + H2O  NH4+ + OH -
Strong Bases v. Weak Bases
Strong Base – a base that completely dissociates to
produce many OH- ions in solution

NaOH, KOH
Weak Base – a base that dissociates to a slight extent
in aqueous solution (not that many OH-)

NH3 (ammonia)
Strength & Weaknesses of A & B Video
Indicators
Indicator Colors for Bases
Litmus paper = blue
Phenolphthalein = pink
Methyl orange = yellow
Measuring the Amount of H+ and OH− Ions in a Solution
_____
pH Scale- measures the _____________
concentration of [H+] ions in a solution
pOH Scale- measures the concentration of [ ____
OH− ] ions in a solution
_____
With the pH scale, we have another way to define acids and bases:
Acids have a pH _________7.0
below
Neutral
Bases have a pH _________7.0
above
=
Neutral pH ___7.0
Acidic
Basic
pH of different household items



Make predictions on whether a solution would be acidic,
basic or neutral
Go around the room, checking each cup with pH paper
(make sure used pH paper goes in GARBAGE!)
 to save pH paper, use HALF a side for each one.
Approximate pH colors:
purple-ish red (pH 2)
red (pH 4)
brown (pH 6)
Stays the same (pH 7)
green (pH 8)
blue (pH 10)
Examples of Common Acids
citrus juices, ___________,
aspirin stomach acid,
Pepsi, _________
battery acid, _____________,
______
vinegar
DNA
Examples of Common Bases
Milk of magnesia, ___________,
ammonia drain cleaner, soap, blood,
____________
________.
antacid tablets, ___________
baking soda
Acids &
Bases pH
video
Exit Slip

When using litmus paper, what color would it turn for an
acid?

If something has a pH of 7, what is it considered?
Calculating pH and pOH
Strong Acids vs. Weak Acids
Strong Acids and Strong Bases

Since they ______________
disassociate…
completely
…so when HCl is placed in water…
100 molecules of HCl are dissolved in water,
100
H+ ions
100
Cl- ions
__________and
__________ions
are produced.
This comes into play for calculating the pH for strong
solutions!
Measuring the Amount of H+ and OH− Ions in a Solution
_____
pH Scale- measures the _____________
concentration of [H+] ions in a solution
pOH Scale- measures the concentration of [ ____
OH− ] ions in a solution
_____
Formulas
pH = − (log [H+])
[H+] = 10−pH
pOH = −(log [OH−])
[OH−] = 10−pOH
pH + pOH = 14
With the pH scale, we have another way to define acids and bases:
below
Acids have a pH _________7.0
above
Bases have a pH _________7.0
=
Neutral pH ___7.0
[H+] = concentration of hydrogen ions 
Molarity
_______________
(M)!
Before we
try
calculating
pH’s, watch
video about
background
information
on pH
Example of Calculating pH
a) Calculate the pH of a 0.001 M HCl solution (so 0.001 H+ ions)
pH = − (log 0.001 M)
[H+] = 0.001 M
pH = 3
b) What is the pOH of a solution with a pH of 3?
pH + pOH = 14
3+ pOH = 14
pOH = 11
c) What is the concentration of [OH−] ions in the solution?
[OH−] = 10−pOH
[OH−] = 10−11 M or 1 x 10−11 M
pH = − (log [H+])
[H+] = 10−pH
pOH = −(log [OH−])
[OH−] = 10−pOH
pH + pOH = 14
You Try:
a) Calculate the pOH of a NaOH solution that has a pH of 8.50
pH + pOH = 14
8.5 + pOH = 14
pOH = 5.5
b) What is the [OH−] of this solution?
[OH−] = 10−pOH
[OH−] = 10−5.5 M or 3.16 x 10−6 M
c) What is the concentration of [H+] ions in the solution?
[H+] = 10−pH
[H+] = 10−8.5 M or 3.16 x 10−9 M
pH = − (log [H+])
[H+] = 10−pH
pOH = −(log [OH−])
[OH−] = 10−pOH
pH + pOH = 14
Exit Slip
Which disassociates to more H+ ions: a strong acid or
a weak acid?
Calculate the pH of .005 M HCl solution
Calculate the pOH of a solution with a pH of 6.
pH = − (log [H+])
[H+] = 10−pH
pOH = −(log [OH−])
[OH−] = 10−pOH
pH + pOH = 14
Acid & Bases Intro to Calculations Answers
1) concentration
2) Concentration of H+ (or Hydronium) Ions
3) Concentration of H+ (or Hydronium) ions
1. a. –log(.005)  2.3
b. –log(2)  -.301
2. a. 5, A
b. 12, B
c. 7, N
d. 10, A
3. a. 10-1.04  0.0912
b. 1013.1  1.26 x 10-13
4. a. –log(.4)  0.398
b. –log(4)  -0.602
*Calculating out a negative pH value does happen when
concentrations are above 1.0 M (so for a very concentrated
acid)
Recognizing Acids & Bases
Neutralization
Recognizing Acids & Bases
 Acids start with the element: _______________
hydrogen

Bases generally have the polyatomic ion:
hydroxide
_________________

Another common base: NH3 ammonia!
Hydroxide: OHHydrogen: H+
Conjugate Acid-Base Pairs
 Conjugate ______Acid substance formed when a _______
base gains a
[H+] ion.
 Conjugate ______Base substance formed when an ______
acid loses a [H+]
ion.
Practice Problems: Label the acid & base on the left side of the
reaction and the conjugate acid & conjugate base on the right side.
a) HCl + H2O  H3O+ + Cl−
acid
base
C.A.
C.B.
______
______
______
______
b) NH3 + H2O  NH4+ + OH−
_____
base
______
acid
______
C.A.
______
C.B.
Neutralization Reactions


Strong acid solutions contain: H+ ions
Strong base solutions contians: OH- ions
Neutralization reaction: an acid-base reaction that has initial
concentrations and volume of reactants equal.
Equal H+ and OH-  NEUTRAL solution (pH = 7)
Neutralization Reactions
salt
When an acid and base are mixed, the reaction produces a _______
water
and ___________.
 All neutralization reactions are ___________
replacement
double
reactions.
MX
H2O
HX + M(OH)  ______
+ ______
(“Salt”)
Neutralization (or Acid-Base Reaction)
Hydrochloric acid reacts with
Sodium hydroxide…
NaCl
H2O (l)
HCl (aq) + NaOH (aq)  _________
+ __________
Salt
Neutralization Video
•an ionic compound produced
from a neutralization reaction
•composed of equal amount of
cations & anions
•thus neutral
•can be aqueous or depending
on solubility may be a precipitate
Alka-Seltzer Activity
Each group needs: 1 small (150 or 250 mL) beaker,
1 alka-seltzer tablet, 1 pH paper
2)
The Indicator is in the front table, add your 10 to 15
drops and then return it to the front!
Vinegar will be at the lab stations.
3)
When you add
1)
3 dropper fulls of vinegar!!
*When finished, you may pick up a study guide for the quiz
on Wednesday! (will have class time tomorrow to
work on the study guide).
Titration
A titration is a technique to determine the concentration of
a solution (mixes acids and bases)
Known concentration is delivered by
a buret to an unknown concentration
and an indicator is used to determine
when neutralization has occurred.
The end point or the equivalence point
is the point of neutralization.

H+ ions = OH- ions
Determining the Concentration of an Acid (or Base) by Titration
MacidVacid = MbaseVbase
A 25 mL solution of HNO3 is neutralized by 18 mL of 1.0 M NaOH
standard solution using phenolphthalein as an indicator. What is
the concentration of the HNO3 solution?
( Macid ) x ( 25 mL ) = ( 1.0 M ) x ( 18 mL )
Macid = 0.72 M
Determining the Concentration of an Acid (or Base) by Titration
You Try
How many mL of 2.0 M KOH will it take to neutralize 55 mL of a
0.76 M HCl standard solution?
A 0.05 L solution of HNO3 is neutralized by 0.025 L of 1.5 M NaOH
standard solution using phenolphthalein as an indicator. What is
the concentration of the HNO3 solution?
Exit Slip
How many mL of 1.5 M KOH will it take to neutralize
150 mL of a 0.75 M HCl standard solution?
What is the pH of a solution has a 1.0M concentration
of H+ ions?
If you could be a strong acid, weak acid, strong base,
weak base, giraffe, kangaroo or the moon, which
would you be and why?
Exit Slip
Label the acid, base, conjugate acid and conjugate base
HF +
H2O  H3O+
+
F−
Answer Key Practice II
2. False – there is a small amount of H+, pH measures
concentration of H ions. If you have a high pH there is a
small, if you have a low pH there are more H+ ions
4. A, N, A, B, A, A, B, A, B, A
5)100 mL
6) 0.14 M
7) 0.125 M
8) pH = 10.37, pOH = 3.63, [OH-] = 10-3.63  0.000234 M
9) 25 mL
10) Water and a salt
Semi-answer Key to Acids
*  = indicates that it completely
breaks apart into the ions (the arrows
both ways, indicate that it does not)
4. Hydrofluoric acid, hydrobromic acid, hydroiodic acid, hydrosulfuric acid
1) Phosphoric acid
3) Carbonic acid
5) Nitrous acid
2) Phosphorous acid
4) Hydronitric acid
6) H3P 7) HNO3 8) H2SO3
1) Bariumn Hydroxide
3) Iron (II) Hydroxide
4) NaOH
5) Ca(OH)2
7) A, B, CA, CB
1) Calcium Hydroxide (B) 5) Sulfuric Acid (A)
Prediction: HBr + LiOH  LiBr + H2O
Acids & Bases 2
Strong Acids and Strong Bases

Since they ______________
disassociate…
completely
…so when HCl is placed in water…
100 molecules of HCl are dissolved in water,
100
H+ ions
100
Cl- ions
__________and
__________ions
are produced.
This comes into play for calculating the pH for strong
solutions!
Find the pH of the following solution…
A solution containing 1 mole of hydrochloric
acid in 12 L of water
pH measures ________________________________.
concentration of H+ ions
M = mol/L
M = 1 mol / 12L
M = _____
0.0833 M HCl _____
0.0833 M H+
pH = -log( 0.0833 )
Find the pH of the following solution…
A solution containing 5 moles of HCl in 10 L of water
Find the pH of the following solution…
A solution containing 20 grams of HCl in 10 L of water
Exit Slip
Calculate the pH of a solution
containing 50 grams of HCl in
2.5 L of water.
Measuring the Amount of H+ and OH− Ions in a Solution
_____
pH Scale- measures the _____________
concentration of [H+] ions in a solution
pOH Scale- measures the concentration of [ ____
OH− ] ions in a solution
_____
Formulas
pH = − (log [H+])
[H+] = 10−pH
pOH = −(log [OH−])
[OH−] = 10−pOH
pH + pOH = 14
With the pH scale, we have another way to define acids and bases:
below
Acids have a pH _________7.0
above
Bases have a pH _________7.0
=
Neutral pH ___7.0