Definition of chemical reaction- Chemical reactions are process where a set of chemical compounds converted to the new set of compound.
In this process, the group of substances that involved in the reaction are called reactants and the new compounds that produces are called products. In chemical reactions only exchange of electrons between the components and breaking of chemical bonds take place. It is either endergonic or endergonic reactions. There is no change of nuclei ,means number proton and neutron remain unchanged.
Example: CO2 + H2O -> C6 H12O6
Here carbon dioxide is reacting with water to produce totally different compound called glucose. So, carbon dioxide and water are reactants and glucose is the product. But the properties of the reactants are different from products.
Types of chemical reaction: Generally chemical reactions can be divided into-
1. Combination – Combination is a type of reaction where two or three components are combined together to form new compound. Here new chemical bonds are formed to prepare new substances.
Example of combination reactions are : H2 +Cl2 → 2HCl
Here hydrogen and chlorine are combined together are called hydrogen chloride.
2. Decomposition - Decomposition is an endorsement thermic reaction where single compound is degraded into two or more components. Here energy is required to break down the chemical bonds. It is of three types – thermal decomposition, electrical decomposition, photogenic decomposition.
Examples of decomposition reactions are-
H2O → H2 + O2 . In presence of electrolysis water is decomposed to form hydrogen and oxygen.
3. Single Displacement - Single displacement reactions are type of reaction where one element of a compound is replaced by the other element.
Examples of displacement reactions are-
Cu + ZnCl2 → CuCl2 + Zn
In this reaction copper is an element which replaces zinc. As a result zinc chloride is converted into copper chloride and zinc is separated.
4. Double Displacement - Double displacement is a type of reaction where cations and anions means positive and negative ions are switch their position to produce new compounds.
Examples of displacement reactions are –
AgNO3 + NaCl → AgCl + NaNO3.
In this reaction two compounds are silver nitrate and sodium chloride are made up of positive ions sodium and silver; negative ions are nitrate and chloride. Here positive ion silver is combined with chloride (negative ion) and produces new compound silver nitrate. On the other hand positive ion sodium combined with negative ion nitrate to form sodium nitrate (a new compound).
5. Combustion - Combustion is a chemical reaction where hydrocarbons are oxidized in presence of oxygen to form carbon dioxide and water.
Examples of combustion reactions are-
CH4 + O2 → CO2 + H2O
In this reaction methane undergoes combustion in presence of oxygen to produce carbon dioxide and Water.
6. Redox - It is a chemical reaction where there is transfer of electrons from one species to other takes place.
Examples of redox reactions are-
Zn + Cu++ → Zn++ + Cu.
Reducing agent + oxidizing agent → oxidised + reduced .