CHEMICAL REACTIONS AND EQUATIONS BY TRIPURARI PRAJAPATI.pdf

SYLLABUS OF CHEMISTRY (SCIENCE)
CBSE CLASS 10th STD.
1. CHEMICAL REACTIONS AND EQUATIONS
2. ACIDS, BASES AND SALTS
3. METALS AND NON, METALS
4. CARBON AND IT’S COMPOUNDS

By: Tripurari Prajapati
M.Sc.. Biotechnology
CHAPTER- 1 SCIENCE (CBSE CLASS 10)

CONTENTS
 Chemical Reaction
 Chemical Equation
 Writing an chemical equation
 Balanced Chemical Equation
 Types of Chemical Reaction
 Combination Reaction
 Decomposition Reaction
 Displacement Reaction
 Double Displacement Reaction
 Oxidation And Reduction
 Corrosion
 Rancidity
 Activities
 PYQs

CHEMICAL REACTION
 Chemical reaction are the processes in which new substances with new
properties are formed.
 Eg: The burning of magnesium in air to form magnesium oxide is an example
of a chemical reaction.

REACTANTS
 The substances which take part in chemical reaction (disappear) are
called reactants.
PRODUCTS
 The new substances produced (appear) as a result of chemical
reaction.
Eg: 𝐴𝑔𝑁𝑂3 + 𝑁𝑎𝐶𝑙 → 𝑁𝑎𝑁𝑂3 + 𝐴𝑔𝐶𝑙
REACTANT PRODUCT

Q. Give the name of reactants and products in each cases.
1. 𝐴𝑔𝑁𝑂3 + 𝑁2 2𝑁𝐻3
2. 6𝐶𝑂2 + 6𝐻2𝑂 𝐶6𝐻12𝑂6 + 6𝑂2
3. 𝐶𝑢𝑆𝑂4 + Fe 𝐹𝑒𝑆𝑂4 + Cu
4. 2𝐻2 + 𝑂2 2𝐻2O
5. Zn + HCl 𝑍𝑛𝐶𝑙2 + 𝐻2

Example of chemical reaction in everyday
life
 Photosynthesis
 Combustion
 Respiration
 Rusting
 Digestion

CHARACTERISTICS OF CHEMICAL REACTION
i. Change In State
ii. Change In Color
iii. Evolution Of Gas
iv. Change In Temperature
v. Formation Of Precipitate

CHANGE IN STATE
𝐶𝑂2(g) + 𝐻2𝑂(l) 𝐻2𝐶𝑂3 (l)
C(s) + 𝑂2(g) 𝐶𝑂2(g)
𝐻2(g) + 𝑂2(g) 2𝐻2O(l)

CHANGE IN TEMPERATURE
CaO(s) + 𝐻2𝑂(l) 𝐶𝑎(𝑂𝐻)2(s) + Heat
(Quick lime)
Mint + 𝐻2𝑂(l) Temperature decrease

• A precipitate is a “solid product” which separates out from the solution
during a chemical reaction.

CHEMICAL EQUATION
 The method of representing a chemical reaction with the help of symbols and
formulae of the substances involved in it is known as a chemical equation.
 A chemical equation can be written in 2 forms:
 Word equation
eg: Hydrogen + Oxygen Water
 Symbolic representation
eg: 2𝐻2 + 𝑂2 2𝐻2𝑂

MAKING A CHEMICAL EQUATION MORE
INFORMATIVE
 The physical states of the reactants and products can be represented by
using symbols.
For solid (s)
For liquid (l)
For gas (g)
For aqueous solutions (aq)
Eg: 2Na(s) + 2𝐻2𝑂(l) 2NaOH(aq) + 𝐻2(g) + Heat

 Precipitate can also be represented by using an arrow
pointing downwards ( ).
Eg: 𝑁𝑎2𝑆𝑂4 + 𝐵𝑎𝐶𝑙2 𝑁𝑎𝐶𝑙 + 𝐵𝑎𝑆𝑂4( )
 Gaseous state of an evolved gas can be represented by
using an arrow pointing upward direction ( ).
Eg: Zn + HCl 𝑍𝑛𝐶𝑙2 + 𝐻2( )

TYPES OF CHEMICAL EQUATION
1) Balanced chemical equation
It is an equation for a chemical reaction in which the
number of atoms for each element in the reaction and
the total charge are the same for both the reactants and
the product.
Eg: Zn + 𝐻2𝑆𝑂4 𝑍𝑛𝑆𝑂4+ 𝐻2

2) Unbalanced chemical equation
It is an equation where the number of atoms for elements
and their total charge are not equal in both side.
Eg: Fe + 𝐻2O 𝐹𝑒3𝑂4 + 𝐻2

WHY TO BALANCE A CHEMICAL REACTION
Law of conservation of mass:
 Mass can neither be created nor destroyed in a chemical reaction .
 That is, the total mass of the elements present in the product of the
chemical reaction has to be equal to the total mass of the elements
present in the reactants.
 In other words, the number of atoms of each element remains the
same, before and after a chemical reaction. Hence, we need to
balance a chemical equation.

BALANCING OF CHEMICAL EQUATIONS
• The process of making the number of different types of atoms equal
on both the sides of an equation is called balancing of equation.
HEAT AND TRIAL METHODS

CHEMICAL REACTIONS AND EQUATIONS BY TRIPURARI PRAJAPATI.pdf

Combination Reaction
Decomposition Reaction
Thermal decomposition
Electrolytic decomposition
Photolytic decomposition
Displacement Reaction
Double Displacement Reaction
Oxidation And Reduction

COMBINATION REACTION
• A reaction in which two or more reactants combine to
form a single product, is called combination reaction.
• A + B + C ABC
• A + B AB
Eg: CaO(s) + 𝐻2𝑂(l) 𝐶𝑎(𝑂𝐻)2(aq) + Heat
(Quick lime) (Slaked lime)

Examples of combination reaction
• C(s) + 𝑂2(g) 𝐶𝑂2(g)
• 2𝐻2(g) + 𝑂2(g) 2𝐻2𝑂(l)
• S + 𝑂2 𝑆𝑂2
• 𝑁𝐻3 + 𝐻𝐶𝑙 𝑁𝐻4𝐶𝑙
• 𝑆𝑂2 + 𝑂2 𝑆𝑂3

DECOMPOSITION REACTION
• A reaction in which a single reactant breaks down to form
two or more products, is known as decomposition reaction.
• ABC A + B + C
• AB A + B
Eg: 𝐶𝑎𝐶𝑂3(s) 𝐶𝑎𝑂 𝑠 + 𝐶𝑂2(g)
(Limestone) (Quick lime)
Heat

Examples of decomposition reaction
• 2𝐹𝑒𝑆𝑂4(s) 𝐹𝑒2𝑂3(s) + 𝑆𝑂2(g) + 𝑆𝑂3(g)
(Ferrous sulphate) (Ferric oxide)
• 2𝑃𝑏(𝑁𝑂3)2(s) 2PbO(s) +4𝑁𝑂2(g) + 𝑂2(g)
(Lead nitrate) (Lead oxide) (Nitrogen dioxide) (Oxygen)
• 2AgCl(s) 2Ag(s) + 𝐶𝑙2(g)
Silver chloride Grey
Heat
Heat
Sunlight

Types of decomposition reaction
1. Thermal decomposition :
Those reactions use the energy in the form of heat for
decomposition of the reactant.
Eg: 𝐶𝑎𝐶𝑂3(s) 𝐶𝑎𝑂 𝑠 + 𝐶𝑂2(g)
(Limestone) (Quick lime)
Heat

2. Electrolytic decomposition :
These reaction involve the use of electrical energy for the
decomposition of the reactant molecules.
Eg: 2𝐻2𝑂 2𝐻2 + 𝑂2
2NaCl 2NaOH + 𝐻2 + 𝐶𝑙2
Electric current
Electric current

3. Photolytic decomposition :
These reaction involve the use of light energy for the purpose of
decomposition.
Eg: 2NaCl 2𝑁𝑎 + 𝐶𝑙2
𝑂3 𝑔 𝑂2 (𝑔) + 𝑂
Photons
Photons

Exothermic and Endothermic Reaction
Exothermic Reaction :
The reaction which are accompanied by the evolution of heat are called
Exothermic Reaction.
Or
The reactions in which heat is released along with the formation of products
are called exothermic reactions.
Eg: 𝐶𝐻4 + 2𝑂2 𝐶𝑂2 + 2𝐻2𝑂 + Heat

Endothermic Reaction :
The reaction which occur by the absorption of heat/energy are
called endothermic reaction.
Eg: 6𝐶𝑂2 + 12 𝐻2𝑂 𝐶6𝐻12𝑂6 + 6𝑂2 + 6𝐻2𝑂

SINGLE DISPLACEMENT REACTION
When a more reactive element displace less reactive element from its
compound, it is called displacement reaction.
Eg: A +BC AC + B

DOUBLE DISPLACEMENT REACTION
Those reactions in which two compounds react by an exchange
by ions to form two new compounds are called double
displacement reaction. Also called as precipitate reaction.
Eg: 𝑁𝑎2𝑆𝑂4 + 𝐵𝑎𝐶𝑙2 𝐵𝑎𝑆𝑂4 + 2𝑁𝑎𝐶𝑙 s

NEUTRALIZATION REACTION
The reaction in which acid react with base to form Salt and water
are called neutralization reaction.
Eg: NaOH + 𝐻2𝑆𝑂4 𝑁𝑎2𝑆𝑂4 + 𝐻2𝑂

OXIDATION REACTIONS
• If a substance gains oxygen and looses hydrogen then
it is said to be oxidation.
Eg : 2Mg + 𝑂2 2MgO

REDUCTION REACTION
If a substance gains hydrogen and looses oxygen then it
is said to be reduction reaction.
Eg: CuO + 𝐻2 Cu + 𝐻2O

REDOX REACTION
When one reactant gets oxidized while the other gets
reduced during a reaction.
Eg:

EFFECTS OF REDOX REACTION IN EVERYDAY
LIFE
1. RANCIDITY :
When fats and oils are oxidized, they become rancid and their
smell and taste change.
Prevention:
Air tight containers, refrigeration, adding antioxidents.
Eg: Butter, Cheese, Chips etc

2. CORROSION :
A metal when attacked by substances around it such as acids etc,
it is said to corrode and this process is known as corrosion.
Eg: Rusting of iron
Prevention :
By painting, grease or oil

ACTIVITIES
2Mg + O2 2MgO
When magnesium ribbon is burning, what do
you observe?
Ans) Magnesium ribbon burns with a dazzling
flame and white powder is collected on the
watch glass placed under it. The white powder
is magnesium oxide formed by the reaction of
magnesium and oxygen present in the air.
Activity 1.1

Question :
1. Why should a magnesium ribbon be cleaned before burning in air?
Ans : Magnesium ribbon comes in contact with 𝐶𝑂2 and 𝑂2 present in air and forms
basic magnesium oxide. The reaction is combination reaction as a new product is
formed. The layer of oxide formed does not allow Mg to burn easily. Hence
magnesium ribbon be cleaned before burning in air.
Mg + 𝑂2 → Mgo
2Mg + 𝐶𝑂2 → 2MgO + C

Activity 1.2
Q. what do you observe when potassium iodide solution is
added to lead nitrate solution in a test tube?
Ans) White lead nitrate reacts with white potassium iodide to
form yellow lead iodide which is insoluble in water.
𝑃𝑏(𝑁𝑂3)2 (aq) + 2KI(aq) → 2𝐾𝑁𝑂3(aq) + 𝑃𝑏𝐼2(s)
Yellow ppt

Activity 1.3
Q. What happens to zinc granules when
dilute hydrochloric acid or sulphuric acid is
added to it? Is there any change in its
temperature?
Zinc being an active metal readily reacts
with dil. hydrochloric acid at room
temperature to form soluble zinc chloride
and hydrogen. We can observe bubbles of
hydrogen gas being formed around zinc
granules. If we touch the conical flask, we
can feel a sense of hotness as there is a
rise in temperature. So, it’s a exothermic
reaction.
Zn + 2HCl → 𝑍𝑛𝐶𝑙2 + 𝐻2

When zinc granules are added to dilute sulphuric acid, there
occurs a change in the state of zinc granules and they are
converted to zinc sulphate (𝑍𝑛𝑆𝑂4) and hydrogen gas is evolved.
Zn + 𝐻2𝑆𝑂4 → 𝑍𝑛𝑆𝑂4 + 𝐻2
This reaction is exothermic, i.e., it involves release of heat and so
the flask becomes hot and temperature of the system increases.

Activity 1.4
Q. Is there any change in temperature when water is added to calcium oxide or quick lime in a
beaker?
Ans) Calcium oxide reacts vigorously with water to produce slaked lime (calcium hydroxide)
releasing a large amount of heat.
In this reaction, calcium oxide and water combine to form a single product, calcium hydroxide.
Such a reaction in which a single product is formed from two or more reactants is known as a
combination reaction.

Do you observe any change in the colour of
ferrous sulphate crystals when they are heated in
the boiling tube over the flame of a burner or spirit
lamp?
Ans) The green colour of ferrous sulphate
crystals changes to brownish black oxide and
smell of burning sulphur will be observed. Ferrous
sulphate decomposes to form ferric oxide
( 𝐹𝑒2𝑂3 ), sulphur dioxide ( 𝑆𝑂2 ) and sulphur
trioxide (𝑆𝑂3 ). So, the gas emitted smells like
burning sulphur. In this reaction, the single
reactant 𝐹𝑒𝑆𝑂4 decomposes to form three
different products. So, the reaction is a
decomposition reaction.
Activity 1.5

Activity 1.6
What do you observe when a boiling test tube
containing lead nitrate powder is heated it over a
flame?
Ans) On heating lead nitrate decomposes with a
crackling sound along with the evolution of brown
fumes of nitrogen dioxide(NO2) which has an
irritating smell. The gas turns blue Litmus red;
hence, it is acidic in nature. A yellow solid residue
of lead oxide (PbO) remains in the test tube.

Activity 1.7
What do you observe when electrolysis of water
happens using simple set up shown in figure
Ans) The breakdown of water happens as shown in the
reaction below :-
When we bring a burning candle at cathode, it burns
immediately but gas at anode does not burn.
At cathode(-ve electrode), hydrogen gas is collected.
At anode(+ve electrode), oxygen gas is collected
At cathode, The collected amount of gas is doubled
rather than gas collected at anode, because during
breakdown of water releases 2 Hydrogen molecule
and 1 Oxygen molecule
2H2O(I) → 2H2(g) + O2 (g)

Activity 1.8
What do you observe when silver chloride is left out in
sunlight for sometime?
Ans) On decomposition, The colour of silver chloride
changes colour which is white, changes it to grey
sunlight
2AgCI (s) → 2Ag(s) + CI2 (g)
(white) (grey)
Silver chloride decomposes into silver and chlorine.
so, the decomposition reaction takes place in the presence of sunlight, it is called Photolysis.
Other examples are:-
sunlight
2AgBr (s) → 2Ag(s) + Br2 (g)
(Brown) (grey)

Activity 1.9
What will happen if leave a iron nail in copper sulphate
solution?
Ans)After 20 mins, The intensity of blue in copper
sulphate decreases compared to normal copper sulphate
solution
Fe(s) + CuSO4(aq) → FeSO4(aq) + Cu(s)
(Copper sulphate) (Iron sulphate)
(Blue) (Green)

Activity 1.10
What do you observe while mixing 3ml of sodium
sulphate and 3ml of barium chloride?
Ans)
The insoluble white substance formed is known as a
precipitate.
Na2SO4(aq) + BaCI2(aq) → BaSO4(s) + 2NaCI(aq)
This is also known as Precipitation Reaction.

Activity 1.11
What will happen 1g of copper powder is
heated?
Ans) The surface of copper powder becomes coated with
black copper oxide. This is because of the oxidation
of copper.
2Cu + 𝑂2 → 2CuO
Copper(II) oxide
(Black Coating)
heat

If we pass hydrogen gas overheated copper oxide (CuO) the black coating
on the surface turns brown as the reverse reaction takes place and copper is
obtained.
CuO+𝐻2→ Cu + 𝐻2O
(Brown)
In the above reaction, copper oxide is reduced to copper, and Hydrogen is
Oxidized to Water. This is a redox reaction.

Previous Years Questions
Q. A reddish brown coloured metal, used in electrical wires, when powdered and heated strongly in an open
china dish its colour turns blacks. When hydrogen gas is passed over this black substance, it regains its original
colour. Based on above information answer the following question.
(i) Name the metal and the black coloured substance formed.
(ii) Write balanced chemical equation for both the equation. [CBSE 2012]
(i) Reddish brown metal is copper. When it is heated in china dish presence of oxygen, black
coloured copper oxidised is formed.
(ii) 2Cu + O₂ → 2CuO
When hydrogen gas is passed over heated copper oxide reddish brown copper metal is formed.
CuO + H₂ → Cu + H₂O

Q. What is redox reaction? Identifying the substance oxidised and the substance
reduced in the following reactions:
(i) 2PbO + C → Pb + CO₂
(ii) MnO₂ + 4HCl → MnCl₂ + H₂O + Cl₂. [CBSE 2012]
Those reactions in which oxidation and reduction take place simultaneously are
called redox reaction.
(i) Pbo is getting reduced and C is getting oxidised.
(ii) MnO₂ is getting reduced. HCL is getting oxidised.

Q. What is rancidity? Mention any two ways by which rancidity can be
prevented. [CBSE 2012]
The process in which taste and smell of food gets spoiled is called
rancidity. It happens due to oxidation.
Prevention from rancidity:
(i) Antioxidants are added to fatty acid to prevent oxidation e.g. chips
are packed in the presence of Nitrogen gas which prevents spoilage by
oxidation.
(ii) Food should be kept in airtight container in refrigerator.

Q. Write balanced chemical equation for the reaction that take place during respiration.
Identifying the type of combination reaction that take place during this process and justifying
the name. Give one more example of this type of reaction. [CBSE 2012]
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + heat
It is exothermic combination reaction because heat is being evolved.
CH₄ + 2O₂ → CO₂ + 2H₂O
Combustion of methane is another example of exothermic combination reaction.

Q. What is meant by: (i) Displacement reaction (ii) Reduction reaction (iii)
Combination reaction. Write balanced chemical equation for each reaction. [CBSE
2012, 2011]
(i) Those reactions in which a more active element displaces a less active element
from its compound are called displacement reaction.
Example: Zn(s) + CuSO₄(aq) → ZnSO₄(aq) + Cu(s)
(ii) The reaction in which hydrogen is added or oxygen is removed or gain of electrons
take place.
Example: Fe⁺⁺⁺ + e– → Fe⁺⁺
(iii) The reaction in which two or more element or compound combine together to
form a single compound are called Combination reaction.
Example: C(s) + O₂(g) → CO₂(g)

Q.
(a) Why is respiration consider as exothermic reaction?
(b) Define the terms Oxidation and reduction?
(c) Identify the substance that is oxidised and reduced in the reaction:
CuO + Zn → Cu + ZnO. [CBSE 2011]
(a) It is because heat is evolved during respiration.
(b) Oxidation is a process in which O₂ or H₂ is removed or loss of electron
take place reduction is a process in which hydrogen is added or oxygen is
removed or gain of electron take place.
(c) Zn is getting oxidised, CuO is getting reduced.

Q. 2g of lid nitrate powder is taken in a boiling tube. The boiling tube is
heated over a flame now answer the following:
(i) State the colour of the fumes evolved and the residue left.
(ii) Name the type of chemical reaction that has taken place stating its
balanced chemical equation. [CBSE 2012]
Sol: (i) Brown coloured fumes of No₂ gas are evolved and yellowish brown
reside is formed.
(ii) Decomposition reaction has taken place as,
2Pb(NO₃)₂ → 2PbO + 4NO₂ +O₂

Q. (i) Classsify the following reaction into different type: (a) AgNO3 + NaCl
→ AgCl + NaNO3 (b) CaO + H2O → Ca(OH)2 (c) 2KClO3 → 2KCl + 3O2. (ii)
Which of the above reaction are precipitation reaction? Why is a reaction
called precipitation reaction? [CBSE 2011]
Sol: (i)
(a) Precipitation reaction(Double Displacement reaction)
(b) Combination reaction
(c) Decomposition reaction
(ii) It is precipitation reaction because one the product formed is in soluble in
water

Q. Classify the following chemical reactions as exothermic or endothermic:
(i) Water is added to quick lime.
(ii) Dilute sulphuric acid is added to zinc granules.
(iii) When ammonium chloride is dissolved in water in a test tube it becomes cold.
(iv) The decomposition of vegetable matter into compost.
(v) Electrolysis of water. (vi) Silver chloride turns grey in the presence of sunlight to
form silver metal. [CBSE 2016]
(i) Water is added to quick lime — Exothermic
(ii) Dilute sulphuric acid is added to zinc granules – Exothermic
(iii)When ammonium chloride is dissolved in water in a test tube it becomes cold — Endothermic
(iv) The decomposition of vegetable matter into compost — Endothermic
(v) Electrolysis of water – Endothermic

Q. Take 3g of barium hydroxide in a test tube, now add amount 2g of ammonium
chloride and mix the contents with the help of the glass rod. Now touch the test
tube from outside. (i) What do you feel on touching the test tube? (ii) State the
inference about the type of reaction occurred. (iii) Write the balanced chemical
equation of the reaction involved. [CBSE 2016]
Sol:-
(i) The test tube becomes hot.
(ii) It is a decomposition reaction.
(iii) 2NH₄Cl + Ba(OH)₂ → BaCl₂ + 2NH₃ + 2H₂O

Q. You must have tasted or smelt the fat containing food material left for a
longtime. Such foods taste and smell bad. What is the reason for this? Name to
the phenomenon responsible for it. List two majors for its Preventions. [CBSE
2016]
Sol:-
Food material left for a long time is oxidised by atmospheric oxygen. This changes the smell
and taste of food.
Majors for prevention:
(i) Keep the food in air tight container.
(ii) Flush the food packets with nitrogen gas before sealing it.

Q. Name the type of chemical reactions represented by the following equation:
(i) CaCO₃ CaO + CO₂.
(ii) CaO + H₂O → Ca(OH)₂.
(iii) Zn + H₂SO₄→ ZnSO₄ + H₂. [CBSE 2017]
Sol:-
(i) CaCO₃ CaO + CO₂
This is a decomposition reaction.
(ii) CaO + H₂O → Ca(OH)₂
This is a combination reaction.
(iii) Zn + H₂SO₄→ ZnSO₄ + H₂
This is a displacement reaction.

Q. Write chemical equation for the reaction taking place when:
(i) Mangnesium react dil. HNO₃.
(ii) Sodium react with water.
(iii) Zinc react with hydrochloric acid. [CBSE 2016]
Sol:
(i) Mg + 2HNO₃(dil) → Mg(NO₃)₂ + H₂
(ii) 2Na + 2H₂O → 2NaOH + H₂
(iii) Zn + 2HCL → ZnCl₂ + H₂

Q. Classify the following chemical reactions as exothermic or endothermic:
(i) Water is added to quick lime.
(ii) Dilute sulphuric acid is added to zinc granules.
(iii)When ammonium chloride is dissolved in water in a test tube it becomes cold.
(iv) The decomposition of vegetable matter into compost.
(v) Electrolysis of water. (vi) Silver chloride turns grey in the presence of sunlight to
form silver metal. [CBSE 2017]
Sol:-
(i) Water is added to quick lime — Exothermic
(ii) Dilute sulphuric acid is added to zinc granules – Exothermic
(iii)When ammonium chloride is dissolved in water in a test tube it becomes cold — Endothermic
(iv) The decomposition of vegetable matter into compost — Endothermic
(v) Electrolysis of water – Endothermic

Q. Decomposition reaction require energy either in the form of heat
or light or electricity for breaking down down the reactants. Write
one equation each for decomposition reaction where energy is
supplied in the form of heat, light and electicity. [CBSE 2018]
Sol:
• Energy supplied in the form of heat:
Ca(OH)₂(aq) → CaO(s) + H₂O(l)
• Energy supplied in the form of light:
2AgCl(s) → 2Ag(s) + Cl₂
• Energy supplied in the form of electricity:
2H₂O → 2H₂ + O₂

Q. (a) What is balanced chemical equation? Why should chemical equation be balanced?
(b) Write the chemical equation of the reaction in which the following changes has taken place:
(i) Change in colour.
(ii) Change in temperature.
(iii) Formation of precipitate. [CBSE 2017]
Sol:- (a) A chemical equation in which the total mass of the reactant is equal to the total mass of the
product is called a balance chemical equation. It may also be defining as a chemical equation in which
the number of atom of each element is equal on the reactant side as well as on the product side. It is
only after balancing the chemical equation that we can find out how much of each product will be
formed from certain quantities of the reactant, in terms of law of conservation of mass.
(b) Chemical Equation corresponding to different changes are given below:
(i) Change in colour:
Fe + CuSO₄ → FeSO₄ + Cu
(ii) Change in temperature:
CaO(s) + H₂O(l) → Ca(OH)₂(aq) + Heat
(iii) Formation of precipitate:
BaCl₂ + Na₂SO₄ → BaSO₄ + 2NaCl

Q. (a) Balance the chemical equation:
(i) NaOH + H2So4 → Na2So4 + H2O.
(ii) PbO + C→ Pb + CO2.
(iii) Fe2O3 + Al → Al2O3 + Fe + Heat.
(b) Write the balanced chemical equation for the following reaction:
(i) Barrium chloride + Potassium sulphate → Barrium sulphate.
(ii) Zinc + Silver nitrate → Zinc nitrate + silver. [CBSE 2016]
Sol:-
(a)
(i) 2NaOH + H₂So4 → Na₂SO₄ + 2H₂O
(ii) 2PbO + C→ 2Pb + CO₂
(iii) Fe₂O₃ + 2Al → Al₂O₃ + 2Fe + Heat
(b)
(i) BaCl₂ + K₂SO₄ → BaSO₄ + 2KCL
(ii) Zn + 2AgNO₃ → Zn(NO₃)₂ + 2Ag

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