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.
--> 2H2(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
let’s go step by step.
Predict the products when solid iron(II) oxide decomposes.
|1. Write the formula for the given reactant.
|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) +
Oxygen is diatomic, so it is written with a subscript
|3. Balance the equation.
||2FeO(s) --> 2Fe(s)