- Definition
of an acid
- Acids
are compounds that can donate H+ ions in water solutions.
The role of water is essential in this definition. Pure HF is
not considered to be an acid. It must be dissolved in water to
act like an acid. There are many different acids, but they all
have something in common. They have hydrogen
attached to a nonmetal from either group 6A or group 7A. This
last idea makes it easier to identify acids.
-
- Binary
acids that have hydrogen combined with an atom form either group
7A or 6A. The examples of binary acids are:
-
-
HF,
HCl, HBr, HI, H2S and H2O.
- It
may be difficult to picture water as an acid but under certain
conditions the water molecule breaks up to form H+ ions
and OH- ions. This is one of nature's tricks. Pure
water is not typically considered very acidic, because an OH-
ions is released along with every H+ ion.
-
- Ternary
acids contain three elements. These types of acids have hydrogen
attached to oxygen. The oxygen is conected to a central atom.
Examples of common ternary acids are:
-
-
HNO3,
HNO2, H2SO4, H2 SO3,
H3PO4, H3PO3, H2
CO3
-
- You
should see a common characteristic in these acids. They all have
a nonmetal element as a central atom. They all have oxygens that
are bridges between the hydrogen and the central atom. The reason
these substances are acids is that the connection or bond between
H and O is weak in these compounds. The bond breaks with the formation
of a H+ ion and a polyatomic anion.
-
|
nitric
acid
|
|
water
|
|
proton
|
|
nitrate
ion
|
HNO3+
H2O ---> H1+
(aq) + NO31- (aq)
-
The
(aq) means the ion is dissolved in water. The ion is in an aqueous
mixture.
- The
oxy acids or ternary acids have their origins in oxides of the
nonmetals like CO2(gas). The strange thing about this
is that these nonmetal oxides form acids when they mix with water.
These compounds are the villains that cause the acid rain problem.
-
-
|
carbon
dioxide
|
|
water
|
|
carbonic
acid
|
|
CO2
|
+
H2O
|
--->
H2CO3 (aq)
|
- Polyprotic
acids
- Acids
with more than one acidic proton/hydrogen can release all of the
protons. This means H2SO4 has two acidic
hydrogens that can be released form each formula unit.
-
|
sulfuric
acid
|
|
water
|
|
two
protons
|
|
sulfate
ion
|
|
H2SO4
|
+
|
H2O
|
------->
|
2
H+ (aq)
|
+
|
SO42-(aq)
|
The
(aq) means the particle is dissolved in water. The particle
is in an aqueous mixture.
-
- Non-acidic
hydrogens
- These
ideas explain why compounds like butane are not
acids
even though there are many hydrogen atoms in the formula. The
hydrogen is attached to carbon which is in group 4A not the required
6A or 7A. The hydrogen atoms are strongly bonded to a nonmetal
atom that doesn't attract electrons to stabilize a negative charge.
-
-
CH3CH2CH2CH3.
|
- Definition
of a base
- Bases
are compounds that can readily donate OH-1 ions
in water solutions.
The role of water is essential in this definition. Pure solids
like NaOH must be dissolved in water to act like a base. There
are many different bases, but they have something in common. They
all have an OH1- and a metal. This last idea makes it easier to
identify bases.
-
- Bases
have a hydroxide ion combined with a metal. The examples of bases
are:
-
-
LiOH,
KOH, NaOH, CsOH, RbOH and H2O.
-
Mg(OH)2,
Ca(OH)2, Ba(OH)2, Sr(OH)2
-
Al(OH)3,
Sn(OH)2, Pb(OH)2,
Fe(OH)2, Fe(OH)3
-
- You
should see a common characteristic in these acids. They all have
a nonmetal element as a central atom. They all have oxygens that
are bridges between the hydrogen and the central atom. The reason
these substances are acids is that the connection or bond between
H and O is weak in these compounds. The bond breaks with the formation
of a H+ ion and a polyatomic anion.
-
|
magnesium
hydroxide
|
|
water
|
|
magnesium
ion
|
|
hydroxide
ion
|
|
Mg(OH)2
|
+
|
H2O
|
---->
|
Mg
2+
(aq)
|
+
|
2
OH1- (aq)
|
The
(aq) means the ion is dissolved in water. The ions are in an
aqueous mixture. The water does not get balanced
|
