Download PDF chemical reactions and equations class 10 Notes

chemical reactions and equations class 10 notes In which we will learn about chemical reactions, chemical equations, types of chemical reactions, combination reactions, decomposition reactions, displacement reactions, exothermic and endothermic, oxidation and reduction reactions, etc.

chemical reactions and equations class 10 notes

 Chemical Reaction :-

Such changes in which substances with new properties are formed are called chemical reactions.

Example:- Digestion of food, respiration, rusting of iron, burning of magnesium ribbon, formation of curd etc.

Identification of chemical reaction :-

These are the factors that help to know that a chemical reaction has taken place:-

  • change in state of matter,
  • change color of matter,
  • heat development,
  • heat absorption,
  • gas evolution,
  • development of light

️ Reagents :-

The substances which take part in a chemical reaction are called reactants.

Products :-

those substances which are made in a chemical reaction are called products.

Chemical Equations :-

A brief representation of a chemical reaction through symbols and formulas of the substances (reactants and products) participating in it is called a chemical equation.

  • Chemical reactions are represented by chemical equations.

  • In a chemical equation, the symbols of the elements or the chemical formulas of the reactants and products are written along with their physical states.

  • The necessary conditions in a chemical reaction such as temperature, pressure, catalyst etc. are shown above or below the arrow mark.

️ Balanced Chemical Equations :-

Such a chemical equation in which the number of atoms of each element is equal on both the sides (left and right side) is called balanced chemical equation.

Importance of balanced chemical equation :-

Law of Conservation of Mass: In any chemical reaction, mass is neither created nor destroyed.

The number of atoms of each element should be the same before (reactant) and after (product) of a chemical reaction.

class 10 science chapter 1 notes


Step-by-step balancing of chemical equations (hit and trial method) :-

Step 1 :-

Write a chemical equation and draw a box around each formula.

Do not change anything inside the box while balancing.

Step 2:-

Note down the number of atoms of different elements present in the equation.

Download PDF chemical reactions and equations Notes
Download PDF chemical reactions and equations Notes

step 3:-

Balance the element with the largest number of atoms by applying improper coefficients on the side of the reactant or product.

Fe +4 H₂O → Fe₃O₄ + 4 H₂

step 4 :-

Balance the atoms of all the elements as in step 3.

3 Fe + 4 H₂O → Fe₃O₄ + 4 H₂

The number of atoms of all elements is the same on both sides of the reaction.

Step 5 :-

Writing the physical states of the reactants and products :-

  • Solid :- ( s )
  • Liquid :- ( l )
  • Gaseous State :- ( g )
  • Aqueous solution :- ( aq )

3Fe ( s ) + 4H₂O( g ) → Fe₂O₄ + 4H₂( g )

Step 6 :-

  • Write some necessary conditions like temperature, pressure or catalyst etc. above or below the arrow mark.

  • The number of atoms of the elements on both sides of the equation is equal. So this equation is now balanced.

  • This method of balancing chemical equations is called hit and trial method because we try to balance the equation using the smallest integer number of coefficients.

types of chemical reactions class 10 notes

️ 1. Combination Reaction :-

A chemical reaction in which two or more substances (elements or compounds) combine to form a single product is called a combination reaction. No by-products are formed in these reactions.

Example :-

  • Combustion of Coal :- C( s ) +0₂( g ) → CO₂( g)
  • Formation of water :- 2H₂( g ) +0₂( g ) + 2H₂0 ( l )
  • (slaked lime) CaO( s ) + H₂O ( l ) → Ca(OH₂) , ( aq ) (slaked lime )

 exothermic chemical reaction:

The reactions in which heat is also released along with the formation of products are called exothermic chemical reactions.

Example :-

  • Combustion of natural gas :- CH₄( g ) +0₂( g ) → CO₂( g ) + 2H₂O( g ) + heat

  • Respiration is an exothermic reaction :- C₆H₁₂0₆( aq ) + 60₂( g ) → 6C0₂( aq ) + 6H₂0 + heat

2. Decomposition reactions :-

A chemical reaction in which a single reactant breaks down to form two or more products is called a decomposition reaction.

There are three types of decomposition reactions :-

  • Thermal Dissociation:- The dissociation done by heat.
  • Electrical Dissipation: - Dissociation caused by the flow of electric current.
  • Optical Dissociation:- Dissociation occurring in the presence of sunlight.

endothermic reaction:

The reactions which require heat, light or electrical energy to break down the reactants are called endothermic reactions.

️ 3. Displacement reaction :-

In these reactions, the more reactive element displaces the less reactive element from its compound.

Example:- Brown copper coating on iron nail :-

Fe(s)+CuSO₄(aq) → FeSO₄(aq)+Cu(s)

A brown copper layer was deposited on the iron nail. The green color of the blue solution of Cuso4 is due to the formation of Feso₄.

     Zn + Cuso₄ → ZnSO₄ + Cu

Zinc is a more reactive element than copper.

️ 4. Double displacement reaction :-

The products in this reaction are formed by the exchange of ions between two compounds.

Na₂so₂ (aq) (sodium sulfate) + BaCl₂ (aq) (barium chloride) → BaSO₄(s) (barium sulfate) + 2Nacl (sodium chloride)

A white insoluble precipitate of barium sulphate (Baso₄) is formed. That is why this reaction is also called precipitation reaction.

️ 5. Reduction and Reduction :-

Selection :-

If there is an increase of oxygen or loss of hydrogen in a substance or both, then it is called oxidation.

Example :-

 C + 0₂→ CO₂

2Cu + 0₂→CuO

Reduction :-

If there is loss of oxygen or increase of hydrogen in a substance, it is called reduction.

️ Redox :-

The reaction in which both oxidation and oxidation are taking place is called redox reaction.

effects of oxidation reaction in daily life

️ Corrosion :-

When a metal comes in contact with oxygen, humidity, acid etc., due to which the upper layer of the metal becomes weakly corroded, it is called corrosion.

Example :- Rusting on iron objects, black coating on silver and green coating on copper are examples of corrosion.

Measures to prevent corrosion :-

Metals can be protected from corrosion by coating, electroplating and painting.

️ Pernicious odor :-

Fatty and oily food items, when exposed to air, get anabolized due to which their taste and smell change, it is called pernicious odor.

Measures to prevent foul odor :-

  • by using an oxidizer
  • placing food in an airtight container
  • by nitrogen gas instead of air
  • by cooling

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