NCERT Solutions Class 10th Science Chapter – 1 Chemical Reactions and Equations Notes

June 2, 2022

NCERT Solutions Class 10th Science Chapter – 1 Chemical Reactions and Equations

Textbook	NCERT
Class	10^th
Subject	Science
Chapter	1^st
Chapter Name	Chemical Reactions and Equations
Category	Class 10th Science
Medium	English
Source	Last Doubt

NCERT Solutions Class 10th Science Chapter – 1 Chemical Reactions and Equations Notes In This Chapter we will learn about Chemical Reaction and Equation, Reactions, Simplest Way to Write Word Equation, Balanced equation follow some importance ways, Endothermic, Exothermic, Types of Chemical Reaction and more such things for more knowledge about this Chapters read their Notes.

NCERT Solutions Class 10th Science Chapter – 1 Chemical Reactions and Equations

Chapter – 1

Chemical Reactions and Equations

Notes

Chemical Reaction – The process in which new substances with new properties are formed from one or more substances is called Chemical Reaction.

Reactants – The substances which take part in chemical reaction are called Reactants.

Example –

C_(s) + O₂ → CO_2(g)
In this reaction Carbon (C) and Oxygen (O) are Reactants.

Products – The substances which are formed in a chemical reaction are called Products.

Example

C_(s)+ O₂ → CO_2(g)
In this Reaction Carbon Dioxide (CO₂) is a Product.

Skeleton Equations – Skeleton Equations are usually unbalanced equation but there are few which need not to be balanced as they are already balanced.

Example –

Skeleton Equation	Balanced Equation
C_(s) + O₂ → CO_2(g)	C_(s) + O_2(g) → CO_2(g)
Zn_(s) + H₂SO_4(l) → ZnSO₄ + H_2(g)	Zn_(s) + H₂SO_4(l) → ZnSO₄ + H_2(g)
S_(s) + 0_2(g) → SO_2(g)	S_(s) + O_2(g) → SO₂(g)

Chemical Reaction involves –

1) Change in state
2) Change in colour
3) Change in temperature
4) Evolution of gas

Examples –

(i) Digestion of food
(ii) Respiration
(iii) Rusting of iron
(iv) Burning of Magnesium ribbon
(v) Formation of curd

Ways of Representing a Chemical Reaction

(i) Word Equation
= Zinc + Sulphuric Acid (Reactant) – Zinc sulphate + Hydrogen (Product)

(ii) Chemical Equation
= Zn + H₂SO₄ (Reactant) – ZnSO₄ + H₂ (Product)

Chemical Equation –

A chemical reaction can be represented by chemical equation. It involves uses of symbol of elements or chemical formula of reactant and product with mention of physical state.

The necessary conditions such as temperature, pressure or any catalyst should be written on arrow between reactant and products.

Example – Magnesium is burnt in air to form Magnesium oxide.

2Mg + 0₂ → 2MgO

Balancing Chemical Equation –

• Law of conservation of Mass – Matter can neither be created nor be destroyed in a chemical reaction.

• So number of atoms of the elements involved in chemical reaction should remain same at reactant and product side.

Stepwise Balancing (Hit and Trial)

Step 1 – Write a chemical equation and draw boxes around each formula.
Fe + H₂O → Fe₃0₄ + H₂

• Do not change anything inside the box.

Step 2 – Count the number of atoms of each element on both the sides of chemical equation.

Element	No. of atoms at reactant side	No. of atoms at product side
Fe	1	3
H	2	2
O	1	4

Step 3 – Equalise the number of atoms of element which has maximum number by putting in front of them.
Fe + 4H₂0 → Fe₃0₄ + H₂

Step 4 – Try to equalize all the atoms of elements on reactant and product side by adding coefficient in front of them.
3Fe + 4H₂0 → Fe₃0₄ + 4H₂

• Now all the atoms of elements are equal on both sides.

Step 5 – Write the physical states of reactants and products.
3Fe (s) + 4H₂0 (g) → Fe₃0₄ (s) + 4H₂(g)

Solid state = (s)
Liquid state = (l)
Gaseous state = (g)
Aqueous state = (aq)

Step 6 – Write necessary conditions of temperature, pressure or catalyst on arrow above or below.

Types Of Chemical Reaction

(1) Combination Reaction
(2) Decomposition Reaction
(3) Displacement Reaction
(4) Double Displacement Reaction

1. Combination Reactiong – The reaction in which two or more reactants combine to form a single product.

Examples –

(i) Burning of coal
C _(s) + O_{2 (g)} → CO_{2 (g)}

(ii) Formation of water
2H_{2 (g)} + O_{2 (g)} → 2H₂O _(l)

(iii) CaO _(s) + H₂O _(l) → Ca(OH)₂ _(aq)
Quick lime = CaO
Slaked lime = Ca(OH)₂

Exothermic Reactions – Reaction in which heat is released along with formation of products.

Examples –

(i) Burning of natural gas
CH₄ _(g) + O_{2 (g)} → CO₂ _(g) + 2H₂O _(g) + Heat

(ii) Respiration is also an exothermic reaction.
C₆H₁₂O_{6 (aq)} + 60₂ _(g) → 6CO₂ _(g) + 6H₂O _(l) + energy

2. Decomposition Reactiong – The reaction in which a compound splits into two or more simple substances is called decomposition reaction.

A → B + C

Types of Decomposition

(i) Thermal decomposition
(ii) Electrolytic decomposition
(iii) photolytic decomposition

The decomposition reactions are mostly endothermic in nature. Energy in the form of heat, light or electricity is generally absorbed in these reactions.

(i) Thermal decomposition – When decomposition is carried out by heating.

Example –

(i) 2FeSO₄ _(s) Passing Heat → Fe₂0₃ _(s) + SO₂ _(g) + SO₃ _(g)
Green colour (Ferrous sulphate) = FeSO₄
Red-brown colour (Ferric oxide) = Fe₂0₃

(ii) CaCO_{3 (s)} Passing Heat → CaO _(s) + CO_{2 (g)}
Lime stone = CaCO₃
Quick lime = CaO

(iii) 2Pb(NO₃)_{2 (s)} Passing Heat → 2PbO _(s) + 4NO₂ _(g) + 0₂
lead nitrate = Pb(NO₃)₂
lead oxide = PbO
Nitogen dioxide = NO₂

NCERT Solutions Class 10th Science Chapter - 1 Chemical Reactions and Equations Notes

(iii) Photolytic Decomposition – When decomposition is carried out in presence of sunlight.

Example

2AgCl Passing Sunlight → 2Ag + Cl₂
= Silver chloride turns grey on exposure to sunlight.

2AgBr Passing Sunlight → 2Ag + Br₂
= Above reaction is used in black and white photography.

Endothermic Reactions – The reactions which require energy in the form of heat, light or electricity to break reactants are called endothermic reactions.

4. Double Displacement Reactions – A reaction in which new compounds are formed by mutual exchange of ions between two compounds.

(i) Na₂SO_{4 (aq)} + BaCl₂ _(aq) → BaSO₄ _(s) + 2NaCl _(aq)

Sodium sulphate = Na₂SO₄
Barium chloride = BaCl₂
Barium sulphate = BaSO₄
Sodium chloride = NaCl

White precipitate of BaSO4 is formed, so it is also called precipitation reaction.
Note: All double displacement reactions are not precipitation reactions.

(ii) 2KI + Pb(NO₃)₂ → Pbl₂ + 2KNO₃

Potassium iodide = KI
Lead Nitrate = P(NO₃)₂
Lead iodide (Yellow ppt) = Pbl₂
Potassium nitrate = KNO₃

(iii) 2KBr + BaI₂ → 2KI + BaBr₂

Potassium bromide = KBr
Barium iodide = BaI₂
Potassium iodide = KI
Barium bromide = BaBr₂

Oxidation And Reduction – In the reaction in which the gain of oxygen or reduces the hydrogen from a reactant are known as oxidation and the loses of oxygen or adding of hydrogen from a reactant are known as Reduction. Their are reaction in it both take place are known as Redox reaction.

Reduction –

(i) The addition of hydrogen to reactant.
(ii) The removal of oxygen from a reactant.

Example –

(a) CuO + H₂ Heat → Cu + H₂O
In this reaction CuO is reduces Oxygen(O) and Hydrogen(H) Gain Oxygen(O).

Oxidation –

(i) The addition of oxygen to reactant.
(ii) The removal of hydrogen from a reactant.

Example –

(a) C + 0₂ → CO₂
(b) 2Cu + 0₂ Heat → 2Cu0

In this reactions both are show gaining of Oxygen(O) and this is known as Oxidation.

Effects of Oxidation in Daily Life

1) Corrosion – When a metal is exposed to moisture, air, acid etc. for some time, a layer of hydrated oxide is formed which weakens the metal and hence metal is said to be corroded and this process is known as Corrosion.

Rusting of iron, black coating on silver and green coating on copper are examples of corrosion.
Corrosion can be prevented by galvanization, electroplating or by applying paints.

2) Rancidity – The oxidation of fats and oils when exposed to air is known as rancidity. It leads to bad smell and bad taste of food.

Methods to Prevent Rancidity –

(i) By adding antioxidants
(ii) Keeping food in air tight containers
(iii) Replacing Air by nitrogen
(iv) Refrigeration

NCERT Solution Class 10th Science All Chapters Notes

Chapter 1 – Chemical Reactions and Equations

Chapter 2 – Acids, Bases, and Salts

Chapter 3 – Metals and Non-Metals

Chapter 4 – Carbon and Its Compounds

Chapter 5 – Life Processes

Chapter 6 – Control and Coordination

Chapter 7 – How Do Organisms Reproduce

Chapter 8 – Heredity

Chapter 9 – Light reflection and refraction

Chapter 10 – Human eye and colorful world

Chapter 11 – Electricity