Chemical Reactions and Equations
Reactant :- The substances that undergo chemical change in the reaction are known as reactants.
Product :- The new substance is formed during the reaction known as product.
Magnesium + Oxygen → Magnesium oxide
(Reactants). (Products)
Catalyst :- Any substance that increases the rate of reaction without itself being consumed.
Balanced chemical equations :- The total mass of the elements present in the products of a chemical reaction has to be equal to the total mass of the elements present in the reactants.
Or,
The number of atoms of each element remains the same, before and after a chemical reaction is known as Balanced Chemical Reactions.
For example :- Zn + H2SO4 → ZnSO4 + H2
Types of Chemical Reactions:-
(1) Combination Reaction:- two or more reactants combine to form a new product known as combination reaction.
For example:- 2H2 + O2→ 2H2O
(2) Decomposition Reaction:- a reactant is decomposed to form two or more products known as Decomposition Reaction.
For example :- CaCo3+ Heat → CaO +Co2
Types of decomposition Reaction :-
- Thermolysis :- decomposition occurs by heat
- Electrolysis :- due to current decomposition occurs. For example :- 2H2O → H2+O2
- Photolysis :- Decomposition occurs by Sunlight. For example:- 2AgCl + Sunlight → 2Ag + Cl2
(3) Displacement Reaction:- A more reactive element displaced a less reactive element to form its compound known as displacement reaction
i.e, A + BC → AC + B
For example :- Fe + CuSo4 → FeSo4 + Cu
(4) Double Displacement Reaction:- Those reactions in which there is an exchange of ions between the reactants are called double displacement reactions.
i.e, AB+CD→AD+BC
For example :- NaOH + HCl → NaCl + H20
Types of reaction on the basis of energy flow :-
- Endothermic Reactions:- Heat required for reaction. For example:– CaCO3 + Heat → CaO+ CO2
- Exothermic Reaction:- Heat/Energy release from reaction. For example:- CH4+202→CO2 + H2O + Energy
Note :- The decomposition of vegetable matter into compost is also an example of an exothermic Reaction.
Note :- Photosynthesis is an Endothermic Reaction.
Oxidation :- Gain of oxygen or Loss of Hydrogen or Electron .
For example :- 2Cu + O2 + Heat → 2CuO
Reduction :- Loss of oxygen or Gain of Hydrogen or Electron.
For example :- CuO +H2 + Heat → Cu+H2O.
Redox Reaction :- when oxidation and reduction take place simultaneously in any given reaction it is called redox reaction.
For example :- ZnO + C → Zn + CO
Corrosion :- When a metal is attacked by substances around it such as moisture, acids, etc., it is said to corrode and this process is called corrosion. The black coating on silver and the green coating on copper are other examples of corrosion.
Rancidity :- The oxidation of oils or fats in food resulting in a bad taste and smell is known as rancidity.