Transcript Acids and Bases - Solon City Schools

The Chemistry of
Acids and Bases
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Chemistry I – Chapter 19
Chemistry I HD – Chapter 16
ICP – Chapter 23
Acids
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Have a sour taste. Vinegar is a solution of acetic acid. Citrus
fruits contain citric acid.
React with certain metals to produce hydrogen gas.
React with carbonates and bicarbonates to produce carbon
dioxide gas
Bases
Have a bitter taste.
Feel slippery. Many soaps contain bases.
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ACIDS
• An acid is a compound that increases the
number of hydrogen ions when dissolved
in water (H+) (present as H3O+ ions)
• An acid solution tastes sour
• An acid can change the color of certain
compounds
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What is an ion?
An ion is an atom that has lost or
gained an electron giving it a
positive (+) or negative (-) charge.
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Some Properties of Acids
 Produce H+ (as H3O+) ions in water (the hydronium ion is a
hydrogen ion attached to a water molecule)
 Taste sour
 Corrode metals
 Electrolytes
 React with bases to form a salt and water
 pH is less than 7
 Turns blue litmus paper to red “Blue to Red A-CID”
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USES OF ACIDS
• Citric acid and ascorbic acid (Vitamin C) are found
in orange juice
• Carbonic acid and phosphoric acid give a “bite” to
soft drinks
• Acids in your stomach aid in digestion
• Sulfuric acid is the most widely used industrial acid
in the world. It is used in making metals, paper,
paints, and fertilizers.
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Acid Nomenclature Review
Anion
Ending
No Oxygen
Acid Name
-ide
hydro-(stem)-ic acid
-ate
(stem)-ic acid
-ite
(stem)-ous acid
w/Oxygen
An easy way to remember which goes with which…
“In the cafeteria, you ATE something ICky”
Acid Nomenclature Flowchart
ACIDS
start with 'H'
2 elements
3 elements
hydro- prefix
-ic ending
no hydro- prefix
-ate ending
becomes
-ic ending
-ite ending
becomes
-ous ending
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Acid Nomenclature Review
• HBr (aq)
• H2CO3
• H2SO3

hydrobromic acid

carbonic acid

sulfurous acid
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Acid and Bases
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Acid and Bases
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Acid and Bases
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Some Properties of Bases
 Produce OH- ions in water
 Taste bitter, chalky
 Are electrolytes
 Feel soapy, slippery
 React with acids to form salts and water
 pH greater than 7
 Turns red litmus paper to blue
“Basic Blue”
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Uses of Bases
• Bases are used in soaps (remember,
bases are slippery)
• Bases are used to make paper, in oven
cleaners, and to unclog drains
• Ammonia is a base and is used in
many household cleaners
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Some Common Bases
NaOH
sodium hydroxide
lye
KOH
potassium hydroxide
liquid soap
Ba(OH)2
barium hydroxide
stabilizer for plastics
Mg(OH)2
magnesium hydroxide “MOM” Milk of magnesia
Al(OH)3
aluminum hydroxide
Maalox (antacid)
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Acid/Base definitions
• Definition #1: Arrhenius (traditional)
Acids – produce H+ ions (or hydronium ions
H3O+)
Bases – produce OH- ions
(problem: some bases don’t have hydroxide
ions!)
Arrhenius acid is a substance that produces
H+ (H3O+)
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in water
Arrhenius base is a substance that produces OH- in water
N
E
U
T
R
A
L
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The pH Scale
ACID
0
1
2
3
4
5
6
7
BASE
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9 10 11 12 13 14
Acid and Base strength is measured on
a scale that ranges from 0 to 14.
Let’s get
pHunky!
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The pH scale is a way of
expressing the strength of
acids and bases.
Under 7 = acid
7 = neutral
Over 7 = base
Note: Stronger acids have
lower numbers &
stronger bases have
higher numbers
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What does “pH” mean?
• pH stands for “power of
hydronium ion”
pH of Common
Substances
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Detecting Acids and
Bases
• You can detect an acid using an indicator.
• INDICATOR - A substance that changes
color in the presence of an acid or a base.
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INDICATORS
• Litmus paper is an indicator
An acid turns blue litmus paper red
A base turns red litmus paper blue
• Cabbage juice can be used as an indicator
pH testing
• There are several ways to test pH
–Blue litmus paper (red = acid)
–Red litmus paper (blue = basic)
–pH paper (multi-colored)
–pH meter (7 is neutral, <7 acid, >7
base)
–Universal indicator (multi-colored)
–Indicators like phenolphthalein
–Natural indicators like red cabbage,
radishes
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Paper testing
• Paper tests like litmus paper and pH
paper
– Put a stirring rod into the solution
and stir.
– Take the stirring rod out, and
place a drop of the solution from
the end of the stirring rod onto a
piece of the paper
– Read and record the color
change. Note what the color
indicates.
– You should only use a small
portion of the paper. You can use
one piece of paper for several
tests.
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pH meter
• Tests the voltage of the
electrolyte
• Converts the voltage to
pH
• Very cheap, accurate
• Must be calibrated with
a buffer solution
pH indicators
• Indicators are dyes that can be
added that will change color in
the presence of an acid or base.
• Some indicators only work in a
specific range of pH
• Once the drops are added, the
sample is ruined
• Some dyes are natural, like radish
skin or red cabbage
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Neutralization Reaction
• When an acid and a base are
combined a salt and water are
formed.
• Ex.
HCl + NaOH → NaCl + H2O
(acid) (base)
(salt)
(water)
The pH of the salt should be close
to neutral (pH 7)