Acids & Bases
They are everywhere..
In your food
In your house
EVEN IN YOU!!!!!
What is an acid?
 An acid is a solution that has an
excess of H+ ions. It comes from the
Latin word acidus that means "sharp"
or "sour".
 The more H+ ions, the more acidic
the solution.
Properties of Acids
 Taste sour
 Conduct electricity
 Corrosive, which
means they break
down certain
substances. Many
acids can corrode
fabric, skin, and
paper
Picture from BBC Revision Bites
http://www.bbc.co.uk/schools/ks3bitesize/science/chemistry/acids_b
ases_1.shtml
Properties of Acids
 Some acids react
strongly with metals
and form hydrogen
gas
 React with bases to
form salts and water
 Turn blue litmus
paper red
Picture from BBC Revision Bites
http://www.bbc.co.uk/schools/ks3bitesize/science/chemistry/acids_b
ases_1.shtml
Uses of Acids
 Acetic acid - vinegar
 Citric acid - lemons, limes, &
oranges.
 Ascorbic acid - Vitamin C
which your body needs to
function.
 Sulfuric acid is used in the
production of fertilizers,
steel, paints, plastics, and in
car batteries.
 Hydrochloric acid – stomach
acid
What is a base?
 A base is a solution that has an
excess of OH- ions.
 Another word for base is alkali.
Properties of a Base
 Feel slippery
 Taste bitter
 Caustic, which means
they break down
certain substances.
 Conduct electricity.
(Think alkaline
batteries.)
Properties of a Base
 Do not react with
metals.
 React with acids to
produce salts and water.
 Turns red litmus paper
blue.
Uses of Bases
 Bases – found in soaps,
ammonia, and many
other cleaning products.
 The OH- ions interact
strongly with substances,
such as dirt and grease.
 Chalk and oven cleaner
contain bases.
 Blood is a basic solution.
Acids and Bases – electrical
conductors
 Acids and bases both can conduct
electricity because both contain ions
 Ionic solutions are electrolytes any substance containing free ions
that make the substance electrically
conductive
pH Scale
• pH is a measure of
how acidic or basic a
solution is.
• The pH scale ranges
from 0 to 14.
• Acidic solutions have
pH values below 7
• Solutions with a pH of
0 are very acidic.
pH Scale
• A solution with a pH of
7 is neutral.
• Pure water has a pH
of 7.
• Basic solutions have
pH values above 7.
• Solutions with a pH of
14 are very basic
pH Scale
• A change of 1 pH unit represents a
tenfold change in the acidity of the
solution.
pH Scale
• For example, if one solution has a pH
of 1 and a second solution has a pH
of 2, the first solution is not twice as
acidic as the second—it is ten times
more acidic.
The relationship between H+, OH- and pH
Weak vs. Strong Acids
 Strong acids ionize completely when placed in
water. HCl, HNO3, H2SO4, HClO4, HI, HBr
 HCl  H+ + Cl Weak acids do not ionize completely, they
remain mostly intact and release fewer H+ ions
 CH3COOH
↔ CH3COO- + H+
Weak vs. Strong Baces
 Strong bases ionize completely when placed in
water. NaOH, LiOH, Be(OH)2, Mg(OH)2
 Mg(OH)2  Mg2+ + 2(OH) Strong bases remove more H+ ions when they
are mixed with water (the OH- ions react with
the H + ions)
 Weak bases do not ionize completely, they
remain mostly intact and release fewer OH- ions
and remove fewer H+ ions when they are mixed
with water
 NH3 + H2O
↔ NH4+ + OH-
Acid – Base Reactions
 A reaction
between an acid
and a base is
called
neutralization. An
acid-base mixture
is not as acidic or
basic as the
individual starting
solutions.
Acids and Bases react to form salts
 When an acid and a base react, H+ ions and
OH- ions react to produce water and decrease
the concentration of H+ ions
 The anions and cations that were connected
with the H+ ions and OH- ions react to form
salts.
 NaOH + HCl  Na+ + Cl- + H+ + OH NaOH + HCl  NaCl + H2O
Acid – Base reactions
 Each salt listed in
this table can be
formed by the
reaction between an
acid and a base.
 Salts are very
important chemicals
Serial Dilution
 Serial dilution is the stepwise dilution of a
substance in solution.