Transcript Document

Acids
and
Bases
Acids: Compounds that contain
one or more hydrogen ions
(H+) when dissolved in water
Bases: Compounds that contain
one or more hydroxide ions
(OH-) when dissolved in
water
Arrhenius Acid
A substance that
dissociates in water to
+
form hydrogen ions (H );
that is, an acid increases
the concentration of H+
ions in an aqueous solution
Arrhenius Base
a substance that
dissociates in water to
form hydroxide (OH−)
ions; that is, a base
increases the
concentration of OH− ions
in an aqueous solution.
Bronsted-Lowry Acid
A molecule or ion that is able to lose, or
"donate," a hydrogen cation (proton, H+)
acid+base  conjugate base+conjugate acid.
The conjugate base is the ion or molecule
remaining after the acid has lost a proton,
and the conjugate acid is the species
created when the base accepts the proton.
The reaction can proceed in either forward
or backward direction; in each case, the
acid donates a proton to the base.
Bronsted-Lowry Base
Substance with the
ability to gain, or
"accept," a hydrogen
cation (proton, H+).
Properties of Acids
 Acids taste sour
Acids have a pH lower than 7
Acids effect indicators
Blue litmus turns red
Universal indicator turns red
Acids are proton (hydrogen ion, H+)
donors
 Acids react with active metals,
produce H2
 Acids react with carbonates
 Acids neutralize bases
Acids Have
a pH less
than 7
Acids React with Active Metals
Acids react with active metals to form
salts and hydrogen gas.
Mg + 2HCl  MgCl2 + H2(g)
Acids Neutralize Bases
HCl + NaOH  NaCl + H2O
Neutralization reactions ALWAYS
produce a salt and water.
Acids you must know:
Strong Acids
Weak Acids
Sulfuric acid, H2SO4
Phosphoric acid, H3PO4
Hydrochloric acid, HCl
Acetic acid, HC2H3O2
Nitric acid, HNO3
Sulfuric Acid
Highest volume production of any
chemical in the U.S.
Used in the production of paper
 Used in production of fertilizers
 Used in petroleum refining

Nitric Acid
• Used in the production of
fertilizers
• Used in the production of
explosives
• Nitric acid is a volatile acid
– its reactive components
evaporate easily
• Stains proteins (including
skin!)
Hydrochloric Acid
• Used in the pickling of
steel
• Used to purify magnesium
from sea water
• Part of gastric juice, it
aids in the digestion of
protein
• Sold commercially as
“Muriatic acid”
Phosphoric Acid
o A flavoring agent in sodas
o Used in the manufacture
of detergents
o Used in the manufacture
of fertilizers
o Not a common laboratory
reagent
Acetic Acid
Used in the manufacture of
plastics
Used in making
pharmaceuticals
Acetic acid is the acid
present in vinegar
Acids are Proton Donors
Monoprotic acids
Diprotic acids
Triprotic acids
HCl
H2SO4
H3PO4
HC2H3O2
H2CO3
HNO3
Ionization of HCl and formation
of hydronium ion, H3O+
H2 O +
Proton
acceptor
HCl
Proton
donor

H3O+ + Cl-
Strong Acids vs. Weak Acids
Strong acids are assumed to be 100%
ionized in solution (good proton donors).
HCl
H2SO4
HNO3
Weak acids are usually less than 5%
ionized in solution (poor proton donors).
H3PO4
HC2H3O2
Organic acids
Strong Acid Dissociation
Weak Acid Dissociation
Effects of acid on the Environment
Rainwater is naturally acidic
WHY?
When CO2 (gas) + H2O H2CO3 (aqueous)
react they form
Carbonic acid
Carbon dioxide (from the air) dissolves in
rainwater, producing carbonic acid, a weak
acid
The normal pH of rainwater is about 5.6
Effects of acid on the Environment
• Acid rain is rain with a pH less than
5.
•
Forms when air-polluting gases dissolve
in
• Rainwater
•
• Sulfur dioxide (SO2) Further lowers the pH of rain.
Effects of acid on the Environment
• Environmental Impact
of Acid Rain
• Dependent on local
geology
• Hill Country soil is
rich in limestone
(CaCO3), which is
basic
• Limestone neutralizes
the effect of acid
rain on lakes
Damages Caused by Acid Rain
1) Damage to aquatic life
•
•
In some sensitive lakes and
streams, acidification has
completely eradicated
fish species, such as the
brook trout, leaving these
bodies of water barren.
Hundreds of the lakes in the
Adirondacks have acidity
levels unsuitable for the
survival of fish
Damages Caused by Acid Rain (Cont.)
2.) Damage to vegetation
Damages Caused by Acid Rain (Cont.)
3) Damage to outdoor artwork
(monuments & statues)
Properties of Bases
 Bases taste bitter
Bases have a pH greater than 7
 Bases effect indicators
 Red litmus turns blue
Universal indicator turns blue
Phenolphthalein turns purple
 Bases are proton (H+) acceptors
and usually have hydroxide ions- OH Solutions of bases feel slippery
 Bases neutralize acids
Examples of Bases




Sodium hydroxide (lye), NaOH
Potassium hydroxide, KOH
Magnesium hydroxide, Mg(OH)2
Calcium hydroxide (lime), Ca(OH)2
Bases Effect Indicators
Red litmus paper turns blue
in contact with a base.
Phenolphthalein
turns purple in a
base.
Bases have
a pH
greater
than 7
Bases Neutralize Acids
Milk of Magnesia contains
magnesium hydroxide, Mg(OH)2,
which neutralizes stomach acid,
HCl.
2 HCl + Mg(OH)2
MgCl2 + 2 H2O
Products of Neutralization
HCl + NaOH 
NaCl + H2O
H2SO4 + Ca(OH)2  CaSO4 + 2 H2O
HNO3 + KOH  KNO3 + H2O
The products of neutralization are always
salt and _______.
water
a ______