ACIDS AND BASES
Chemistry Joke
THE BASE IS UNDER A SALT!
ACIDS AND BASES Acids and bases are two classes of
chemical compounds that we encounter frequently in everyday living.
Vinegar and lemon juice are common acids.
Ammonia and bleach are common bases.
Acids and bases have opposite properties and the ability to cancel or neutralize each other.
Almost all acids begin with H+, and most bases end with OH-.
PROPERTIES OF ACIDS Taste sour Are strong or weak
electrolytes React with bases to
form water and salts
React with active metals to produce H2
Turn litmus (and cabbage) red
Low pH
NAMING ACIDS—A REVIEWAnion Endin
gExample Acid Name Example
-ide Cl-, chlorideHydro-(stem)-
icHydrochloric acid,
HCl
-ite SO32-, sulfite (stem)-ous
Sulfurous acid, H2SO3
-ate NO3-, nitrate (stem)-ic Nitric acid, HNO3
PROPERTIES OF BASES Taste bitter Are strong or weak
electrolytes React with acids to
form water and salts Feel slippery Turn litmus (and
cabbage) blue High pH
TWO ACID/BASE THEORIES Arrhenius Bronsted-
Lowry
ARRHENIUS Simplest definition
and most restrictive
Acids supply H+ ions
Bases supply OH- ions
BRONSTED-LOWRY Added to Arrhenius
definition of bases Acids are proton
(H+) donorsBut… Bases are proton
(H+) acceptorsDon’t necessarily
have to supply OH-
NH3 (ammonia) can now be recognized as a base.
CONJUGATE ACID/BASE PAIRS Bronsted-Lowry also defined conjugate
acids and bases. HA + H2O A− + H3O+
HA is an acid. The product A- is its conjugate base.
H2O is behaving as a base. The product H3O+ is its conjugate acid.
These pairs differ by only one H+.The compound with the extra H+ is the acid.
SELF-IONIZATION OF WATER Sometimes when water molecules
collide, a hydrogen ion transfers. H20 + H20 H3O+ + OH-
Hydronium ion Hydroxide ion
Water can act as both an acid and a base, producing both H+ and OH- ions.
Sometimes the self-ionization of water is shown as: H20(l) H+(aq)+ OH-(aq)
H+ and H3O+ are often used interchangeably.
STRONG ACIDS AND BASES Strength in acids and bases does NOT
refer to how corrosive or dangerous they are.
Strong acids and bases dissociate (break apart) completely in water.
At equilibrium, there is no acid or base left that has not ionized (separated into its ions)
One of the most corrosive and dangerous acids, HF, is actually a weak acid.
STRONG VS. WEAK
http://www.mhhe.com/physsci/chemistry/chang7/esp/folder_structure/ac/m2/s1/acm2s1_1.htm
ACID / BASE NEUTRALIZATION
When an acid reacts with a base, both
are neutralized as water and a salt are
produced.
Predict the products and write the
balanced equation for the reaction of
sulfuric acid with potassium hydroxide.
Chemistry Joke
Q: Why do chemistry professors like to teach about ammonia?
A: Because it’s very basic material!