ACIDS BASES
ACID - a proton donor. Ex. An organic acid could be a molecule made
of a string carbon atoms with
a carboxyl group (-COOH) on the end. In a water solution, the concentration
of hydrogen ions floating around
will be
low, and so the carboxyl group donates its hydrogen to the
solution. The hydrogen's electron stays with the carboxyl
group giving it a negative charge,
while
hydrogen's electron stays with the carboxyl
group giving it a negative charge, while the hydrogen ion, or proton, has a
positive charge. BASE - a proton acceptor. An organic base usually has an amine group
(-NH2) attached. Amine groups accept protons from
a water solution that has a high
hydrogen
ion concentration. Accepting
a proton makes
the -NH2 into -NH3.
An acid/base scale has been derived
using
water as the base. Water acts
as an acid
when it gives up one of its hydrogens
to
become a hydroxide(OH-). The hydroxide acts as a base when it accepts a proton to become water. In a sample of pure water, the number of
hydrogen ions equals the number
of hydroxide,
which is defined as a neutral
solution. The
hydrogen ion concentration of
a neutral sample
of water is 1 x 10to the power of (-7) moles/ liter. MOLE - a group containing 6 x 10 23 things. A liter of water would also have the
same concentration of hydroxides,
1 X 10
-7 moles/liter. The acid/base level is made
by taking the negative logarithm
of the hydrogen
ion concentration, which is 7. The pH of water is 7. If the acid may add to the water, it may donate protons. If the hydrogen concentration reduced tenfold
to 1 X 10 to the power of -6
moles/liter,
the pH would be then 6. If the base were add, it would accept protons from the water.
If the proton concentration reduced
tenfold,
the hydrogen ion concentratio
would be 1
X 10 to the power of -8 moles/liter
for a
pH of 8.
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MOLECULES - two or more atoms bonded together by sharing
electrons so that each
atoms has full shells.
An oxygen atom - atomic number 8 - has two and six electrons
in its first and second shells. Hydrogen- atomic number 1 - has one electron in its frist shell. If
2 Hydrogen atoms were to each put their electrons next to an electron in Oxygen's second shell,
then all three atoms would "think"
that they had full shells. The shell model
representation is only dimensional.
Covalent Bond - sharing of electrons. 2 similar atoms in
a molecule would share electrons equally.
An example is along strand carbon atoms in
which the bond between eac carbon is composed
of two equally shared electrons.
POLAR Covalent bond - unequally share of electrons. This type
of bond has a negative and a positive end.
Sodium ion & Chlorine ion stick together - opposite charges attract.
If a group of sodium ion and chlorine ions would stick together. They would not form
a molecule because ionic bonds do not have a direction; they would form
a crystal, also called ionic solid. A polar molecule like water, and an ionic substance, like salt, will
interact because of their charges. A solution
can be made by adding salt (the solute) to water( the solvent). A cluster of water molecules will line up with their positive sides towards
each negative chlorine ion and loosen each chlorine from the crystal.
Each positive sodium ion will also become
surrounded by water molecules. The positive sodium and negative chlorine ions drift independently through the solution
surrounded by spheres of water molecules.
The polar attractions described are not bonds but merely attractions,
and as such, they are not nearly as strong
as covalent or ionic bond.
To be continued on my review and I will post more. Wish me luck on my exam next week!!!
Ciao!
