Another example is potassium phosphate (K3PO4):
Milligram molecular weight = 212 mg
Total positive valence = 3
Milligram equivalent weight = 212 mg = 70.7 mg
3
In a reaction, one milliequivalent (mEq) weight of one compound will react with one
milliequivalent weight of another. If we are reacting two compounds, then, we can
determine how much of each compound should be used to obtain a desired amount of
product.
2-7.
OXIDATION-REDUCTION REACTIONS
Previously, we have examined the processes involved in writing, balancing, and
interpreting reactions and looked at examples of several types of reactions. One type of
reaction we did not examine closely was the oxidation-reduction reaction (sometimes
called redox reaction). Even though this type of reaction is very important in the
chemistry of drug molecules, it is beyond the scope of our instruction to study them in
detail. However, a basic understanding of this process will be valuable to you in
understanding many of the incompatibilities, storage problems, and some disease
states that you will encounter later.
a. Review of Valence. Before these reactions are studied, valence should be
reviewed briefly. The following two valence concepts are especially important in
oxidation-reduction reactions:
(1) All elements in their free and uncombined state are considered to have a
valence of zero. This holds even for those elements that are diatomic molecules in their
free state.
(2) All atoms can exist in a number of valence states. The common
valences which you learned previously are the preferred and most stable valences
under normal conditions, but other valences can and do occur.
(3) These two concepts are important because oxidation-reduction reactions
always involve a change in the valence numbers of some of the elements involved in
the reaction.
b. Oxidation. Oxidation, in inorganic chemistry, is defined as the loss of
electrons or an increase in the valence of an element. Consider, for example, the
oxidation of elemental iron:
-
FeO-2e
---> Fe+2
MD0803
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