Acids, Bases and pH
What do you notice about the
compounds below?
Characteristics of Acids
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An acid is a substance that produces hydrogen ions
(H +) in a solution.
Common Properties of Acids:
– taste sour
– form electrolyte solutions
– corrosive
– react with indicators = turns blue litmus paper red
Remember..
What is a solution?
– A homogeneous mixture (evenly mixed)
What is an electrolyte?
– It is a solution that will conduct
electricity, remember ions have a
charge!!
Common Acids
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Gastric Acid - found in your stomach to help
with digestion.
Sulfuric Acid - used in dehydrates, batteries,
and fertilizer.
Nitric Acid - used in fertilizer and explosives
Carbonic Acid is used to make soft drinks.
What do these things have in
common?
Characteristics of Bases
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A base is a substance that produces
hydroxide ions (OH-) in solution.
Common Properties of Bases
– taste bitter
– feel slippery
– crystals when dissolved
– form electrolyte solutions
– Corrosive
– react with indicators, turns red litmus paper blue
Common Bases
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Soap, Ammonia, Hydroxides.
Sodium Carbonate is baking soda
Ammonia used as a cleaner, with a strong
smell
Borax, a detergent
Sodium Hydroxide is used for manufacturing
chemicals and paper production.
How do you determine
strength or weakness?
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Since acids and bases produce ions in
solution, we measure the strength of the
solution by how well the ions dissociate (or
dissolve in solution).
If the ions completely dissociate you get a
strong acid or base.
If the ions do not dissociate well, the acid
or base is weak.
Strong and Weak Acids

Strong acid: nearly all the acid molecules
dissociate into ions
 Example:

HCl, Sulfuric Acid
Weak acid: only a small fraction of molecules
dissolve in water
 Example:
vinegar
Strong and Weak Bases

Strong base: Dissociates completely in a
solution.
 Example:

Sodium hydroxide
Weak base: does not dissociate completely in a
solution
 Example:
ammonia
pH of a Solution – The pH Scale
The pH of a solution is a measure of the
concentration of H+ ions in it.
 The pH measures how acidic or basic a
solution is.
 The greater the H+ concentration is, the
lower the pH is and the more acidic the
solution is.
 As you increase or decrease 1 number in pH it
really changes by 10 X not 1.

Reading a pH Scale
pH Scale ranges from 0 to 14
 Less than 7 = Acid
 Equal to 7 = neutral
 Greater than 7 = Base

14
0
7
INCREASING NEUTRAL
ACIDITY
INCREASING
BASICITY
How to remember what’s what
Acid comes before Base in the
alphabet
 Low numbers come before high
numbers
 Each increase/decrease in number is
an increase/decrease in strength BY
10 X, not 1.

pH Scale
pH of Common Substances
pH scale …again
The scale ranges from
0-14 with increasing
strength as you move
away from neutral.
A substance with a pH of
below 7 is an acid.
A substance with a pH of
above 7 is a base.
A substance with a pH of
7 is neutral.
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Some Common Examples:
Hydrochloric Acid (HCl): pH = 1.1
Sulfuric Acid: pH = 1.2
Carbonic Acid: pH = 3.8
Sodium Carbonate : pH = 8.5
Ammonia : pH = 11.0
Borax : pH = 9.5
Sodium Hydroxide : pH = 13.8