Mind Map Chemical Reaction and Equation:
Following are the changes which are responsible for the chemical reaction.
- change in state
- change in colour
- evolution of gas
- change in temperature
Reactants:
- The substances or chemicals which undergo chemical changes during the reaction are called as reactants.
Products:
- After reactants undergoes chemical reaction, they form the new substances or compounds called as products.
For example:
Magnesium + Oxygen —> Magnesium oxide
Here, magnesium and oxygen are reactants while magnesium oxide is the product formed. The chemical equation given is called as chemical reaction.
Balanced chemical equation:
The chemical reaction is said to be balanced only when the number of atoms of each element remains the same before and after the completion of the chemical reaction.
For example:
3Fe(s) + 4 H2O(g) —> Fe3O4(s) + 4 H2O(g)
This is the balanced chemical reaction.
Types of chemical reaction:
1.) Combination reaction:
The chemical reaction in which one or two reactants reacts together to form the single compound is called as combination reaction.
For example:
Cao(s) + H2O(l) —> Ca(OH)2 + Heat
- In above chemical reaction, calcium oxide and water react together to form the single product as calcium hydroxide.
Following are also the examples of combination reaction.
i) Burning of coal:
C(s) + O2(g) —> CO2(g)
ii) Formation of water:
2H2(g) + O2(g) —> 2H2O(l)
Exothermic chemical reaction:
- The chemical reaction in which more amount of heat is evolved after the product formed such a chemical reaction is called as exothermic chemical reaction.
For example:
Burning of natural gas:
CH4(g) + 2O2(g)—-> CO2(g) + 2H2O(g)
- When vegetables get decomposed into the compost then also more heat is released such reaction is also the exothermic chemical reaction.
2.) Decomposition reaction:
- The chemical reaction in which the single compound reactant get broken down into simpler and simpler form as a product such a chemical reaction is called as decomposition reaction.
For example:
2FeSO4(s)—-> Fe2O3(s) + SO2(g) + SO3(g)
- When ferrous sulphate is heated it loses water and its colour get changed and forms the sulphur dioxide and also sulphur trioxide.
CaCO3(s) ——>CaO(s) + CO2(g)
- Calcium carbonate which is called as limestone when heated get decomposed into calcium oxide named as lime or quick lime and carbon dioxide gas.
- The decomposition reaction which takes place with the help of heat are called as thermal decomposition reaction.
- When silver chloride gets decomposed into silver and chlorine with the help of light then it turns grey in the presence of sunlight.
The decomposition reaction occurs is as given below.
2AgCl(s) —–> 2Ag(s) + Cl2(g)
- In similar manner silver bromide get decomposed into silver and bromine as given below.
2AgBr(s) —-> 2Ag(s) + Br2(g)
- The decomposition of silver bromide reaction is mainly used in black and white photography.
- All the decomposition reactions require some energy which is in the form of heat or light to break the reactant molecule into the product form. So, decomposition reactions are the endothermic reactions as they need heat to decompose.
Endothermic chemical reactions:
The chemical reaction in which heat is required to complete the reaction and to form the product are called as endothermic reactions.
3.) Displacement reaction:
- The chemical reaction in which one of the element or group of the reactant molecule get removed or displaced by the other element or group and finally reaction get completed to form the product. Such a chemical reaction is called as displacement reaction.
For example:
Fe(s) + CuSO4(aq) —-> FeSO4(aq) + Cu(s)
In the above chemical reaction, Fe displaces or removed the Cu from copper sulphate solution and forms the iron sulphate as the product. This is the displacement reaction.
- The most reactive elements than copper are zinc and lead which displaces copper from its compound more easily.
- The following chemical reaction shows the displacement reaction.
Zn(s) + CuSO4(aq) —-> ZnSO4(aq) + Cu(s)
Pb(s) + CuCl2(aq) —–> PbCl2(aq) + Cu(s)
4.) Double displacement reaction:
- The chemical reaction in which a precipitate is formed is called as precipitate reaction.
- And the chemical reaction in which exchange of ions takes place between the reactant molecule and the products are formed is called as double displacement reaction.
For example:
When sodium sulphate and barium chloride react with each other then exchange of SO42- and Cl22- ions takes to form the precipitate of BaSO4 as given in the chemical reaction given below.
Na2SO4(aq) + BaCl2(aq) —-> BaSO4(s) + 2NaCl(aq)
Oxidation and reduction:
- The chemical reaction in which oxygen is gained or hydrogen is removed during the chemical reaction is called as oxidation reaction.
- And the chemical reaction in which hydrogen is gained or oxygen is removed during the chemical reaction is called as reduction reaction.
2Cu + O2 —–> 2CuO
- This is the oxidation reaction as oxygen is taken in forming the product.
- Here, Cu get oxidised.
CuO + H2 —–> Cu + H2O
- This is the reduction reaction as hydrogen is gained during the formation of products.
- Here, Cu get reduced.
Redox or oxidative-reduction reaction:
- The chemical reaction in which simultaneous oxidation and reduction reaction takes place is called as oxidation-reduction or redox reaction.
- In redox reaction, one reactant gets reduced while other get oxidised simultaneously.
For example:
CuO + H2 —–> Cu + H2O
- Here, Cu get reduced by loosing oxygen while H2 get oxidised by gaining oxygen to form H2O molecule. Hence, there is simultaneous oxidation and reduction reaction takes place called as redox reaction.
- Another example of redox reaction is as given below.
ZnO + C —-> Zn + CO
MnO4 + 4HCl —-> MnCl2+ 2H2O + Cl2
Following are the effects of oxidation reactions in everyday life:
1.) Corrosion:
- The new iron articles get reddish in colour after sometime due to environmental effects called as rusting of an iron. When metals get in contact with moisture or acids then it is called as corrode and the process is called as corrosion.
- Corrosion leads to damage of metals which used in making bridges, buildings, ships, iron railings etc.
2.) Rancidity:
- Sometimes food containing fats and oils get oxidised and due to which their taste and smell get changed. This is called as rancidity. To avoid the rancidity i.e. to avoid oxidation some antioxidant are added to the food containing fats and oils.