NCERT Solutions For Class 10 Science Chapter 1 Chemical reactions And Equations

NCERT Exercises are one of the most important parts of class 10 students as these questions are from the examination point of view for CBSE Board exams. Here at SidClasses we provide you with one of the best NCERT solutions for Class 10 Science Chapter 1 Chemical reactions And Equations that you can consider for your notes for the board exam.

Chemical reactions involve the transformation of one or more substances into new substances with different properties. Chemical equations are a shorthand way of representing a chemical reaction, using symbols and formulas to show the reactants, products, and quantities of each. In class 10 science, students learn about balancing chemical equations, types of chemical reactions, and factors affecting the rate of chemical reactions. They also study the law of conservation of mass, which states that the total mass of the reactants in a chemical reaction is equal to the total mass of the products.

Class 10 Science Chapter 1 NCERT Exercise

Question 1

Which of the given statements about the reaction below is incorrect?

2PbO (s) + C(s) → 2Pb (s) + CO₂ (g)

a. Lead is getting reduced
b. Carbon dioxide is getting oxidized
c. Carbon is getting oxidized
d. Lead oxide is getting reduced

(i) (a) and (b)
(ii) (a) and (c)
(iii) (a), (b) and (c)
(iv) all

Solution – Option (i) (a) and (b)

Question 2

[ Fe₂O₃ + 2Al → Al₂O₃ + 2Fe ]

The above reaction is an example of a
(i). Combination reaction
(ii). Double displacement reaction
(iii). Decomposition reaction
(iv). Displacement reaction

Solution – Option (iv). Displacement Reaction

Question 3

What happens when dilute hydrochloric acid is added to iron fillings? Tick the correct answer

a. Hydrogen gas and iron chloride are produced
b. Chlorine gas and iron hydroxide are produced
c. No reaction takes place
d Iron salt and water are produced

Solution – Option (a) Hydrogen gas and iron chloride are produced

Question 4

What is a balanced chemical equation? Why should chemical equations be balanced?

Solution- A balanced chemical equation is an equation in which the total charge and the number of atoms for each element in the reaction are the same for both reactants and products.

The chemical equation should be balanced so that it follows the law of conservation of mass.

Question 5

Translate the following statements into chemical equations and then balance them.

a. Hydrogen gas combines with nitrogen to form ammonia
b. Hydrogen sulfide gas burns in the air to give water and sulfur dioxide
c. Barium chloride reacts with Aluminium sulfate to give Aluminium chloride and a precipitate of barium sulphate
d. Potassium metal reacts with water to give potassium hydroxide and hydrogen gas

Solution –

a. 3H₂ + N₂ → 2NH₃

b. 2H₂S + 3O₂ → 2H₂O + 2SO₂

c. 3BaCl₂ + Al₂(SO₄)₃ → 2AlCl₃ + 3BaSO₄

d. 2K + 2H₂O → 2KOH + H₂

Question 6

Balance the following chemical equations.

a. HNO₃ + Ca(OH)₂ → Ca(NO₃)₂ + H₂O
b.NaOH + H₂SO₄ → Na₂SO₄ + H₂O
C. NaCl + AgNO₃ → AgCl + NaNO₃
d. BaCl₂ + H₂SO₄ → BaSO₄ + HCl

Solution –

a. 2HNO₃ + 2Ca(OH)₂ → Ca(NO₃)₂ + 2H₂O

b. 6NaOH + 3H₂SO₄ → 3Na₂SO₄ + 6H₂O

C. NaCl + AgNO₃ → AgCI + NaNO₃

d. BaCl₂ + H₂SO₄ → BaSO₄ + 2HCl

Question 7

Write the balanced chemical equations for the following reactions:

(a) Calcium hydroxide + Carbon dioxide → Calcium carbonate + Water

(b) Zinc + Silver nitrate → Zinc nitrate + Silver

(c) Aluminium + Copper chloride → Aluminium chloride + Copper

(d) Barium chloride + Potassium sulphate → Barium sulphate + Potassium chloride

Solution –

(a) Ca (OH)₂ + CO₂ → CaCO₃ + H2O

(b) Zn + 2AgNO₃ → Zn(NO3)₂ + 2 Ag

(c) 2Al + 3 CuCl₂ → 2AlCl₃ + 3Cu

(d) BaCl₂ + K2SO₄ → BaSO₄ + 2KCl

Question 8

Write the balanced chemical equation for the following and identify the type of reaction of each case.

(a) KBr + BaI₂ → KI + BaBr₂

(b) ZnCO₃ → ZnO + CO₂

(c) H₂ + Cl → HCl

(d) Mg + HCl → MgCl₂ + H₂

Solution-

a. 2KBr + BaI₂ → 2KI + BaBr₂ — Double Displacement reaction

b. ZnCO₃ → ZnO + CO₂ — Decomposition reaction

c. H₂ + Cl₂ → 2HCl — Combination reaction

d. Mg + 2HCl → MgCl₂ + H₂ — Displacement reaction

Question 9

What is meant by exothermic and endothermic reactions? Give examples.

Solution –

Exothermic reaction: The reaction in which heat and energy are released as products are called an exothermic reaction. Eg – Burning of candles, Rusting of iron, Nuclear Fission, etc

Endothermic reaction: The reaction that requires heat and energy to process is called an endothermic reaction. Eg – Photosynthesis, Evaporation, Melting of ice, etc.

Question 10

Why is respiration considered an exothermic reaction?

Solution- During the process of respiration, glucose combines with oxygen in our body cells to form carbon dioxide and water along with lots of heat and energy, which is why respiration is considered an exothermic reaction.

Glucose + oxygen → carbon dioxide + water + energy

Question 11

Why are decomposition reactions called the opposite of combination reactions? Write equations for decomposition reactions.

Solution – In a decomposition reaction, a chemical compound breaks down into two or more products when treated with heat, light, or electricity. For example – ( 2HgO →  2Hg + O₂ ) whereas, in a Combination reaction, two or more chemical compounds react and combine with each other to form a single product. For example – (3H₂ + N₂ → 2NH₃)

Question 12

Write one equation each for decomposition reactions in which energy is supplied in the form of heat, light, or electricity.

Solution –

Question 13

What is the difference between displacement and double displacement reactions? Write relevant equations for the above.

Solution –

Property	Displacement Reaction	Double Displacement Reaction
Definition	A reaction in which an element replaces another element in a compound	A reaction in which two compounds exchange ions or elements to form two new compounds
Products	One compound and one element	Two new compounds
Type of Reaction	Redox Reaction	Acid-Base Reaction or Precipitation Reaction
Examples	Zn + 2HCl → ZnCl2 + H2 Cu + 2AgNO3 → Cu(NO3)2 + 2Ag	AgNO3 + NaCl → AgCl + NaNO3 Na2CO3 + CaCl2 → 2NaCl + CaCO3

Question 14

In the refining of silver, the recovery of silver from silver nitrate solution involves displacement by copper metal. Write down the reaction involved.

Solution – Cu (s) + 2AgNO₃ (aq) → Cu(NO₃)₂ (aq) + 2Ag (s)

Question 15

What do you mean by a precipitation reaction? Explain by giving examples:

Solution – It is a reaction in which cations and anions in an aqueous solution combine together to form an insoluble ionic solid called a precipitate, it is formed out of the solution. For example –

• AgNO₃​(aq)+NaCl(aq)→AgCl(s)↓+NaNO₃​(aq) (Here AgCl is insoluble and is called a precipitate) ;

• AgNO_3 (aq) + KCl_(aq) → AgCl_(s) + KNO_3(aq) (Here AgCl is insoluble and is called a precipitate)

Question 16

A shiny brown coloured element ‘X’ on heating in the air becomes black in colour. Name the element ‘X’ and the black-coloured compound formed.

Solution – The shiny brown-coloured element X is copper metal (Cu). When copper metal is heated in air, it forms a black-coloured compound of copper oxide. So, the black-coloured compound is copper oxide or copper (II) oxide, CuO.

Question 17

Why do we apply paint on iron articles?

Solution – As we know when iron is exposed to water or oxygen, its soft and porous surface is eaten up called rusting. So to prevent this rusting process we apply paint to it.

Question 18

Oil and fat-containing food items are flushed with nitrogen. Why?

Solution – Fat and oil-containing food items are flushed with nitrogen to prevent them from being rancid. When oil and fat-like substances get oxidized in the air, their products give a very foul smell and an unpleasant taste that can result causing various diseases if consumed. So nitrogen acts as an unreactive gas and prevents it from rancidity.

Question 19

Explain the following terms with one example each.
a. Corrosion
b. Rancidity

Solution –

a. Corrosion is the process in which metals are eaten up gradually when exposed to air, moisture, or any chemical on their surface. It is caused due to the oxidation of metals with air.

Example: rusting of iron, etc.

b. Rancidity is a process in which substances like fats and oil get oxidized when exposed to air, resulting in a foul smell and unpleasant taste.

Examples: Rancidity of milk products, rancidity of cooked vegetables, etc

Question 20

Why should a magnesium ribbon be cleaned before burning in the air?

Solution – Magnesium ribbons develop an oxide layer over them with time. So it should be cleaned before burning to facilitate rapid burning.

Question 21

Write the balanced equation for the following chemical reactions.

i. Hydrogen + Chloride → Hydrogen chloride
ii. Barium chloride + Aluminium sulphate → Barium sulphate + Aluminium chloride
iii. Sodium + water → Sodium hydroxide + Hydrogen

Solution –

i. H₂ + Cl₂ → 2HCl
ii. 3BaCl₂ + Al₂(SO₄)₃ → 3BaSO₄ + 2AlCl₃
iii. 2Na + 2H₂O → 2NaOH + H₂

Question 22

Write a balanced chemical equation and state symbols for the following reactions.

a. Solutions of barium chloride and sodium sulphate in water react to give insoluble barium sulphate and the solution of sodium chloride
b. Sodium hydroxide solution (in water) reacts with a hydrochloric acid solution (in water) to produce sodium chloride solution and water.

solution –

(a) BaCl₂ (aq) + Na₂SO₄ (aq) → BaSO₄ + 2NaCl (aq)

(b) NaOH (aq) + HCl (aq) → NaCl (aq) + H₂O

Question 23

A solution of a substance ‘X’ is used for whitewashing.
(i) Name the substance ‘X’ and write its formula.
(ii) Write the reaction of the substance ‘X named above with water

Solution –

(i) Here “X” is Quick Lime and its formula is ( CaO ) (Calcium oxide)

(ii) CaO + H₂O → Ca(OH)₂ (s)

Question 24

Why does the colour of copper sulphate solution change when an iron nail is dipped into it?

Solution – Here copper is being displaced by iron from the copper sulphate solution as iron is more reactive than copper and The deep blue colour of the copper sulphate solution fades due to the formation of a light green solution of iron sulphate. additionally, A red-brown coating of copper metal is formed on the surface of the iron metal.

Question 25

Identify the substances that are oxidised and the substances that are reduced in the following reactions.
i. 4Na(s) + O₂ (g) → 2Na₂O(s)
ii. CuO(s) + H₂(g) → Cu(s) + H₂O(l)

Solution –

i. 4Na(s) + O₂ (g) → 2Na₂O(s)
Here oxygen is added to sodium. Hence, Sodium (Na) is getting oxidized.

ii. CuO(s) + H₂(g) → Cu(s) + H₂O(l)

Here oxygen is being removed from CuO so Cu is getting Reduced and Oxygen is being added to hydrogen so hydrogen is getting oxidised

Class 10 science chapter 1 exercise

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