Chemistry Reference
In-Depth Information
Solution
The proposed reactants are more stable than the desired products because
is insoluble in water, and
CaCO
3
Na
2
CO
3
and
CaCl
2
are both soluble.
Thus, this direct reaction is not feasible.
EXAMPLE 8.14
What type of reaction is each of the steps of the Solvay process?
Solution
In the order shown, the six reactions are classed as (1) decomposition,
(2) combination, (3) double substitution, (4) decomposition, (5) combina-
tion, and (6) double substitution followed by decomposition.
Combustion Reactions
Everyone is familiar with the process called
burning.
Burning, also called
combustion,
is the rapid reaction of a wide variety of materials with oxygen gas.
Combustion reactions of elements can also be classified as combination reactions;
the
type
of reaction is not as important as the
products.
For example, we can refer
to the following reactions as combination reactions or combustion reactions:
C(s)
O
2
(g)£ CO
2
(g)
S(s)
O
2
(g)£ SO
2
(g)
The combustion reactions of
hydrocarbons
—compounds composed of carbon
and hydrogen only—are especially important as sources of useful energy. We
burn methane,
CH
4
,
called natural gas, in our homes to provide heat, and we
combust octane,
C
8
H
18
,
in our cars to provide mechanical energy:
CH
4
(g)
2 O
2
(g)£ CO
2
(g)
2 H
2
O(g)
2 C
8
H
18
(
/
)
17 O
2
(g)£ 16 CO(g)
18 H
2
O(g)
In such reactions, either carbon monoxide or carbon dioxide may be produced,
in addition to water. If sufficient oxygen is present, carbon dioxide is produced.
If the supply of oxygen is limited, as in a car engine, carbon monoxide is the
product. (With very limited oxygen, soot—a form of carbon—and water are
produced.)
In any case, water is a product.
Water is one product of the
combustion of hydrocarbons.
EXAMPLE 8.15
Which of the following reactions was carried out in a limited supply of oxygen?
2 C
6
H
14
(
/
)
19 O
2
(g) £ 12 CO
2
(g)
14 H
2
O(g)
2 C
6
H
10
(
/
)
11 O
2
(g) £ 12 CO(g)
10 H
2
O(g)
