DECOMPOSITION!!

Definition of decomposition : opposite of synthesis, is when a compound is broken down into simpler substances, usually through electrolysis.

An example of decomposition is as follows:

AB --> A + B

In a decomposition reaction a more complex substance breaks down into its more simple parts. One reactant yields 2 or more products. Basically, synthesis and decomposition reactions are opposites.

For example, water can be broken down into hydrogen gas and oxygen gas. The chemical equation for this decomposition reaction looks like:

reactant -------> product + product

To visualize a decomposition reaction look at the following cartoon:




In this cartoon the egg (the reactant), which contained the turtle at one time, now has opened and the turtle (product) and egg shell (product) are now two separate substances.

Some examples of decomposition reactions are shown below:

C12H22O11(s) ----> 12C(s) + 11H2O(g)
Pb(OH)2(cr) ----> PbO(cr) + H2O(g)
2Ag2O(cr) ----> 4Ag(cr) + O2(g)

An example of spontaneous decomposition is that of hydrogen peroxide, which will slowly decompose into water and oxygen.

2H2O2 → 2H2O + O2

Carbonates will decompose when heated, a notable exception being that of carbonic acid, H2CO3. Carbonic acid, the "fizz" in sodas, pop cans and other carbonated beverages, will decompose over time (spontaneously) into carbon dioxide and water

H2CO3 → H2O + CO2

Other carbonates will decompose when heated producing the corresponding metal oxide and carbon dioxide. In the following equation M represents a metal:

MCO3 → MO + CO2