Chemistry Reference
In-Depth Information
to give formic acid
(HCHO
2
)
and chromium(III) ion, as well as other
products.
2
Cr
3
(aq)
CH
3
OH(aq)
Cr
2
O
(aq) £ HCHO
2
(aq)
?
7
Sometimes, a single reactant can act as both oxidizing agent and reducing
agent in the same reaction. Such a reactant is said to undergo autooxidation-
reduction, or
disproportionation.
EXAMPLE 16.15
When gas disproportionates in concentrated NaOH solution, is pro-
duced. What other chlorine-containing compound is produced? Write a balanced
chemical equation for the reaction.
Cl
2
NaClO
3
Solution
Because the chlorine is oxidized to in the sodium chlorate, it must be reduced
to produce the other compound. The only oxidation number lower than zero for
chlorine in
5
Cl
2
is
1,
and the compound is NaCl. The balanced equation is
3 Cl
2
(g)
6 NaOH(aq) £ 5 NaCl(aq)
NaClO
3
(aq)
3 H
2
O(
/
)
Practice Problem 16.15
If exposed to heat or light, or even left stand-
ing, decomposes. What is the oxidizing agent, and what is the reducing
agent? Write a balanced equation for the reaction.
H
2
O
2
Snapshot Review
❒
Be sure to balance the number of atoms of element oxidized or
reduced (in step 1) and balance any “other” elements (step 2) in the
few cases where necessary.
ChemSkill Builder
10.4, 10.5, 10.6
❒
Do not add any species that changes the oxidation state of any
element after step 1.
A. Calculate the change in oxidation number in a species that goes from
(a) to (b) to
B. Complete and balance the following equation:
1
5,
1
1.
H
(aq)
NO
3
(aq) £ Zn
2
(aq)
NH
4
Zn(s)
(aq)
Key Terms
Key terms are defined in the Glossary.
“control” of shared electrons (16.1)
disproportionation (16.4)
half-reaction (16.4)
half-reaction method (16.4)
oxidation (16.4)
oxidation number (16.1)
oxidation-reduction reaction (16.4)
oxidation state (16.1)
oxidizing agent (16.4)
redox reaction (16.4)
reducing agent (16.4)
reduction (16.4)
Stock system (16.2)
