A decomposition reaction is the opposite
of a synthesis reaction. In a decomposition reaction a reactant compound
is broken into two or more less complex substances. you are given a compound
as the reactant. In most cases, to find the product you split the compound
into the individual elements. The other types of decomposition reactions
(decomposition of a hydrate, chlorate, carbonate, etc.) are covered in other
tutorials. This tutorial focuses on the decomposition of a binary compound.
The general pattern of a decomposition reaction is:
AB --> A + B
Look at the example below.
Example #1:
2H2O(l)
--> 2H2(g) +
O2(g)
Water decomposes (usually
with the help of electricity) to form hydrogen gas and oxygen gas. Hydrogen
and oxygen are written with subscripts of 2 because they are both diatomic
molecules.
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Now
let’s go step by step.
Predict the products when solid iron(II) oxide decomposes.
Description
of Action |
Action |
| 1. Write the formula for the given reactant. |
FeO(s) -->
|
| 2. On the products side of the equation, write
the symbols for the two elements in the compound. Be
sure to separate the elements by a + sign. If either of the elements
is diatomic, be sure to write a 2 as its subscript. |
FeO(s) --> Fe(s) +
O2(g)
Oxygen is diatomic, so it is written with a subscript
of 2. |
| 3. Balance the equation. |
2FeO(s) --> 2Fe(s)
+ O2(g) |
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