General Chemistry Principles, Patterns, and Applications, 2011

we assign oxidation states of −2 and +1 to the oxygen and hydrogen atoms, respectively, leading to a net
charge of
[(2 O atoms)(−2)] + [(1 H atom)(+1)] = −3
To obtain an electrically neutral carboxylic acid group, the charge on this carbon must be +3. The
oxidation states of the individual atoms in acetic acid are thus
C − 3 H 3 + 1 C + 3 O 2 − 2 H + 1
Thus the sum of the oxidation states of the two carbon atoms is indeed zero.
Exercise
Assign oxidation states to all atoms in each compound.
a. barium fluoride (BaF 2)
a. formaldehyde (CH 2O)
b. potassium dichromate (K 2Cr 2O 7)
c. cesium oxide (CsO 2)
d. ethanol (CH 3CH 2OH)
Answer:
a. Ba, +2; F, −1
a. C, 0; H, +1; O, −2
b. K, +1; Cr, +6; O, −2
c. Cs, +1; O, −½
d. C, −3; H, +1; C, −1; H, +1; O, −2; H, +1
Oxidants and Reductants
Compounds that are capable of accepting electrons, such as O2 or F2, are
calledoxidants (or oxidizing agents) because they can oxidize other compounds. In the process of
accepting electrons, an oxidant is reduced. Compounds that are capable of donating electrons, such as
sodium metal or cyclohexane (C6H12), are calledreductants (or reducing agents) because they can cause the
reduction of another compound. In the process of donating electrons, a reductant is oxidized. These
relationships are summarized in Equation 3.30:
Equation 3.30
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