Reaction Type: Decomposition
During decomposition, one compound splits apart into two (or more pieces). These pieces can be elements or simpler compounds
Written using generic symbols, it is usually shown as:
AB à A + B
However, that really only works for splitting apart into the elements, like these examples.
HgO à Hg + O2
H2O à H2 + O2
MgCl2 à Mg + Cl2
FeS à Fe + S
Decomposition can also split one compound into two simpler compounds (or compound and an element) as in these examples:
CaCO3 à CaO + CO2
Na2CO3 à Na2O + CO2
KClO3 à KCl + O2
Ba(ClO3)2 à BaCl2 + O2
Notice how, in every case so far, there is only one substance on the left-hand (reactant) side. This is always the case in a decomposition reaction. Don't forget that!!
Figuring out what the products are in decomposition is harder (maybe you'll think it's easier!!) because you will have to recognize several categories of decomposition reactions. Here are your first (yes, there's more!) three:
1) All binary compounds (like the four in the first example set above) will break down into their elements.
2) All carbonates (like the first two in the second example set above) break down to the oxide and carbon dioxide.
3. Chlorates (like KClO3 and Ba(ClO3)2 in the example) will break down to the binary salt and oxygen.