subject: Decomposition Reaction [print this page] In chemistry it can be defined as separation of a substance or materials into two or more substances that might vary from each other and from the original or unique substance. In electrolysis chemistry it can be defined as decomposition reaction synthesized by passing a current via a solution which containing ions.
In other words it can be defined as reaction or chemical reaction in which a substance breakdown into two or more basic components. It is the processes opposite to the chemical synthesis. Whereas in chemical synthesis, which involves molecular bonding so that components (two or more) might to form a compound (single chemical compounds). A well known example of such a reaction is conversion of H2O to hydrogen and oxygen gas (temperature = 212 degree F or 100 degree Celsius).
Classification of Decomposition Reaction
It is usually classified into three types, as follows
Catalytic decomposition e.g. Hydrogen per oxide decomposed into H20 and O2 catalyzed by H2O2
Electrolytic decomposition e.g. a decomposition reactions occurs when aqueous solution exposed to electric current
Thermal decomposition e.g. decomposition reaction occurs in the presence of heat or radiation
Decomposition Reaction Examples
Example 1: carbonates usually decompose to form a metal oxide and CO2.
CaCo3 -->CaO
Example 2: When magnesium carbonate is heated it produces magnesium oxide and carbon dioxide
MgCO3 --> MgO+CO2
Example 3: When ammonia carbonate is heated it produces as follows
(NH4)2CO3--->NH3+H2) +CO2
Example 4. Sodium bicarbonate is heated it produces as follows.
NaHCO3 --> CO2+H2O+Na2CO3
Example 5. Sodium chlorate NaClO3 is heated in the existence of a catalyst it produces as follows.
NaClO3 --> NaCl+O2
Example 6. Potassium chlorate is heated in the presence of catalyst (manganese dioxide) it produces potassium chloride and oxygen.
KClO3-->KCl+O2
Example 7. When solid potassium nitrate is heated
KNO3 -->KNO2+O2
Example 8. Carbonic acid decomposes produces water and carbon dioxide
H2CO3--> H2O+CO2
Decomposition of Water
Decomposition of water takes place only at higher temperature. Though water is a very stable complex, it decomposes faintly (~0.02%) to give hydrogen and oxygen at temperatures greater than 2000C.
The decomposition reactions are of three types of: they are thermal, electrolytic and catalytic decomposition reactions.
The general reaction for chemical decomposition includes:
AB A + B
The exact example being the electrolysis of water to gaseous hydrogen and oxygen:
2H2O (I) 2H2 + O2
Another example for decomposition reactions is that of hydrogen peroxide, which will gradually decompose into water and oxygen:
2H2O2 2H2O + O2
Similarly, Carbonates will decompose when heated to give carbon dioxide and water
H2CO3 H2O + CO2
Rates of decomposition of water
The rates of decomposition of H2O vary with substrate and climate. The organic compounds may be decomposed within a matter of weeks. Decomposition is most rapid in warm and moist environments, such as tropical rainforest, but takes place slowly in cool and or dry conditions.
The decomposition of H2O is theoretically a one step process for the generation of hydrogen molecule. Yet, the straight decomposition of H2O is not practical since it needs extremely high temperatures. So, a two-step process of decomposition of H2O is applied using an oxide as a complex compound to decompose at very low temperature. In recent times, ferrites are used as metal oxides to decompose H2O and carbon dioxide have been used actively. This type of reaction undergoes redox reaction because Ferrite ion behaves both as bivalence and trivalence type.
Introduction to a combination reaction:
A combination reaction or a complex reaction is a general kind of a chemical reaction (the word typically refers to an inorganic chemical reaction), in which two or more reactants species are chemically linked together to construct a solo product. When two or more compound mixtures joined mutually to form a single product, is called as a combination reaction. Several elements act in response with one another in this manner to form compounds.
This type of combination reaction is typically exothermic since when the bond forms between the elements, heat is released. Combination reaction generally have two or more reactants and has only one product produced by it. While a combination reaction takes place between a metal and a nonmetal the product is an ionic solid.
