ACIDS AND BASES
Sections 8.3 and 8.4
Acids
A acid is a compound that produces
hydronium (H3O+) ions when
dissolved in water.
Examples:
HCl – hydrochloric acid
HNO3 – nitric acid
H2SO4 – sulfuric acid
(Notice the hydrogen in the front)
Properties of acids
TASTE SOUR
Things like lemons and oranges, taste sour because they
contain acids.
Do not test solutions by taste.
REACTIVE WITH METALS
A metal changes color when exposed to a substance or
bubbles form in a acid when a metal is placed in it.
CHANGE COLORS IN INDICATORS
An indicator is a substance that changes color in the
presence of an acid or a base
One type of indicator is Litmus paper. Litmus is a dye
made from plants.
Blue litmus turns red in the presence of an acid.
Red Litmus stays red in the presence of an acid.
BASES
A BASE is a compound that produces
hydroxide (OH-) ions when dissolved
in water
Examples:
NaOH – sodium hydroxide
Mg(OH)2 – magnesium hydroxide
Ca(OH)2 – calcium hydroxide
Notice the (OH) in each.
PROPERTIES OF BASES
BITTER TASTE
Cough syrup has a base.
Unsweetened (cooking) chocolate has
a base in it to make it taste bitter.
Again don’t test unknown substances
by taste.
SLIPPERY FEEL
Think about soap when it gets wet.
CHANGES COLORS IN
INDICATORS
Bases turn red litmus paper blue. Blue
litmus stays blue.
Phenolphthalein is another acid and
base indicator. It turns red in base and
stays clear in an acid.
ACID-BASE REACTIONS
A reaction between an acid and a
base is called NEUTRALIZATION.
The reactants are an acid and a base.
The products are water and a salt
(contains a halogen)
An acid loses its hydrogen ion and is
called a proton donor (b/c H+).
A base loses its (OH) and is a proton
acceptor (b/c OH -)
pH Scale
The pH is the
measure of
Hydronium ions in
a substance
Ranges from 0-14
Low pH (0-6.99) is
acidic.
High pH (7.01 -14)
is basic
7 is neutral
Buffers and electrolytes
A Buffer is a solution that doesn’t allow big
changes in pH.
Made from weak acids and weak bases.
An electrolyte is a substance that ionizes or
separates into ions when it dissolves in
water.
Made from strong acids or bases.
Found in sports drinks
Strong and weak acids, bases
Strong acids dissolved in water, ionize
almost completely.
Ph is low.
Strong bases dissolved in water,
dissociate almost completely.
Ph is high.
Weak acids and bases ionize or
dissociate slightly in water.
Ph is near neutral.