NCERT Solutions for Class 10 Science Chapter 1 (Chemical Reactions and Equation)

NCERT Solutions for Class 10 Science Chapter 1 (Chemical Reactions and Equation)

NCERT Solutions for Class 10 Science Chapter 1 – As you all know, This is the first chapter of your class 10th science as well as the first chapter of your class 10th chemistry.

After reading/learning this chapter you will get to know about the various reactions and phenomena that take place in our day to day life. The effect of these phenomena in our life. As well as the Reaction and the science behind these phenomena.

So, basically in this chapter, we are going to deal with the following things. –> What are chemical reactions, how to balance them, Different types of chemical reactions like the combination, Displacement, Double displacement, Redox reactions and etc.

Ncert class 10th chapter-1 (Chemical reactions and equation) have a good weightage in the board exams also. Every year in the Board Exam 3–4 Practise-Based Questions are asked. Trust me this is a very easy chapter and You can really Score very good marks just by reading NCERT only.

So Student let’s start with our today’s topic!

NCERT Solutions for Class 10 Science Chapter 1 (page no. 6)

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

Answer:- Magnesium Ribbon should be cleaned with the Sandpaper before burning in the air. because Magnesium is a very reactive metal and it reacts with the oxygen present in the atmosphere and makes a Protective oxide layer of Magnesium Oxide(MgO) on its surface.

That’s why we need to clean the magnesium Ribbon before burning so that we can remove the Oxide layer from its surface.

NCERT Solutions for Class 10 Science Chapter 1 (Chemical Reactions and Equation) 1


(i) H2+Cl2→2HCl(Balanced)

(ii) 3BaCl2+Al2(SO4)3→2AlCl3+3BaSO4 (Balanced)

(iii) 2Na+2H2O→2NaOH+H2 (Balanced)

NCERT Solutions for Class 10 Science Chapter 1 (Chemical Reactions and Equation) 2

i) BaCl2+Na2SO4→BaSO4+2NaCl

ii) NaOH+HCl→NaCl+H2O

NCERT Solutions for Class 10 Science Chapter 1 (page no. 10)

NCERT Solutions for Class 10 Science Chapter 1 (Chemical Reactions and Equation) 3


i) Substance ‘X’ which is used for whitewashing is quick lime/Calcium Oxide(CaO).

ii) CaO+ H2O → Ca(OH)2 + Heat

2. Why is the amount of gas collected in one of the test tubes in Activity
1.7 double of the amount collected in the other? Name this gas.


Activity 1.7 NCERT Solutions for Class 10 Science Chapter 1
Download NCERT Class 10th ch-1 PDF

In the above activity 1.7, gas collected in one of the test tubes is double the amount of the gas collected in the second one. Because water gets hydrolyzed to release H2 and O2 gas. Here, After electrolysis one molecule of oxygen and two molecules of Oxygen gas are released, That’s why the amount of Hydrogen collected would be double that of oxygen.

Ncert class 10th chapter 1 (Question/Answer page no. 13)

1. Why does the color of copper sulfate solution change when
an iron nail is dipped in it?

Ans:- As you know that copper is less reactive than the Iron, So that’s why When an iron nail dipped in the copper sulfate solution, iron displaces copper from the copper sulfate. Therefore the color of the copper sulfate solution changes. The reaction Equation :

Fe+CuSO4 → FeSO4 +Cu

2. Give an example of a double displacement reaction other than
the one was given in Activity 1.10.

Ans:- Reaction Between silver nitrate ( AgNO3) and Sodium chloride (NaCl) is an example of a double displacement reaction. Here (Ag) Silver donates its ion to Sodium chloride(NaCl) ion and pick up nitrate ion to form silver chloride(AgCl) and Sodium Nitrate(Nano3 [a white color of ppt.])

AgNO3 + NaCl → AgCl + NaNO3

NCERT Solutions for Class 10 Science Chapter 1 (Chemical Reactions and Equation) 4


(1). In the first case, Na is oxidized by gaining O2.

(2). In this case, Hydrogen is getting Oxidized and CuO(Copper oxide) reduced by losing oxygen to form Cu(Copper).

NCERT Solutions for Class 10 Science Chapter 1 :-(Chemical reactions and Equations) [Back Exercise]

NCERT Solutions for Class 10 Science Chapter 1 (Chemical Reactions and Equation) 5

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

Solution: (i) A and B.

Because (a) Oxygen is being removed from lead oxide. (b) Carbon dioxide is oxidized the oxygen atoms removed from lead and added to the Carbon.

NCERT Solutions for Class 10 Science Chapter 1 (Chemical Reactions and Equation) 6

Solution:- (d) Decomposition Reaction,

Explanation: Because, As you know in displacement Reaction the highly reactive metal displaces the lowest reactive Metal from its Position. Similarly, In this case (Fe) is less reactive than the Al. That’s why Al displaces the Fe from Fe2o3 and forms Al2O3 + Fe.

NCERT Solutions for Class 10 Science Chapter 1 (Chemical Reactions and Equation) 7

Answer:- (a). Hydrogen gas (H2) and iron chloride(FeCl2) are produced.

Explanation: 2HCl+Fe→FeCl2+H2, Again the Fe(Iron) is more Reactive than the Hydrogen that’s why here Fe replaces the Hydrogen from its place.

Read this chart, After reading this chart you will be able to understand the following Reactions.

Q4. What is a balanced chemical equation? Why should chemical equations be balanced?

Answer:- The no. of atoms of Each element present in the left side of the Reactant should always be equal to the no. of Atoms present at the Right-hand Side.

It is important to balance a Chemical reaction, To Satisfy the law of Conservation of mass( discovered by Antoine Laurent Lavoisier ) and Also to satisfy the law of Constant Proportion (discovered by Joseph Prous).

NCERT Solutions for Class 10 Science Chapter 1 (Chemical Reactions and Equation) 8

(a) Unbalanced chemical Rxn..: H2+N2→NH3

Balanced Chemical Rxn.: 3H2+N2→2NH3

(b) Unbalanced Rxn: H2S+O2→H2O+SO2

Balanced Rxn: 2H2S+3O2→2H2O+2SO2

(c)  Unbalanced Rxn.: BaCl2+Al2(SO4)3→AlCl3+BaSO4

Balanced Rxn.: 3BaCl2+Al2(SO4)3→2AlCl3+3BaSO4

(d) Unbalanced Rxn.: K+H2O→KOH+H2

Balanced Rxn.:  2K+2H2O→2KOH+H2

6. Balance the following chemical equations.

(1) HNO3 +Ca(OH)2 → Ca(NO3)2 + H2O(Unbalanced)

(2) NaOH + H2SO4 → Na2SO4 + H2O(Unbalanced)

(3) NaCl + AgNO3 → AgCl + NaNO3(Unbalanced)

(4) BaCl2 + H2SO4 → BaSO4 + HCl(Unbalanced)


(1) 2HNO3+2Ca(OH)2→2Ca(NO3)2+2H2O(Balanced)

(2) 6NaOH+3H2SO4→H2SO4+6H2O(Balanced)

(3) NaCl+AgNO3→AgCl+NaNO3(Balanced)

(4) BaCl2+H2SO4→BaSO4+2HCl(Balanced)

7. Write the balanced chemical equation for the following reactions.

1. Calcium hydroxide + Carbon dioxide —-> Calcium carbonate + Water

2. Zinc + Silver nitrate —-> Zinc nitrate + Silver

3. Aluminium + Copper chloride —-> Aluminium chloride + Copper

4. Barium chloride + Potassium sulphate —-> Barium sulphate + Potassium chloride


(a) 2Ca(OH)2+2CO2→2CaCO3+2H2O

(b) Zn+2AgNO3→Zn(NO3)2+2Ag

(c) 2Al+3CuCl3→2AlCl3+3Cu

(d) BaCl2+K2SO4→BaSO4+2KCl

8) Write a balanced chemical equation for the following and identify the type of reaction of each case






2KBr+BaI2→2KI+BaBr2 (This is a Double Displacement Reaction)

ZnCO3→ZnO+CO2 (This is a Decomposition Reaction)

H2+Cl→2HCl  (This is a Combination Reaction)

Mg+2HCl→MgCl2+H2 (This is displacement Reaction)

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

Ans:- Exothermic Reaction:- This is a type of reaction in which the Heat releases at the time of Reaction. Ex:- (Combustion, Thermit Reaction, Etc.)

Endothermic Reaction:- In this reaction, the energy absorbed from the surrounding. or During this reaction, the Energy is Absorbed. Ex;- (Melting ice cubes. Melting solid salts. Evaporating liquid water.)

10. Why is respiration considered to be an exothermic reaction?


Ans:- Respiration is considered as Exothermic Reaction because for the energy we eat food that provides us the Energy. Through the process of digestion, the food molecules breakdown in the form of molecules like Glucose. These substances come in contact with the Oxygen present in our body cells to form Carbon dioxide & water along with a certain amount of energy(This is called Respiration).

Since the energy in the form of heat (that maintains our body temperature) the respiration is considered to be an exothermic reaction.

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

Answer:- Decomposition reaction is the opposite of the combination Reaction because In Combination Reaction the two ar more Elements combine to form Single Compound. Ex:- (A + B —.>AB).

Where in the Decomposition reaction the one Compound is broken down into two or more than two Elements. Ex:- ( AB—> A+B).

Also, In most of the cases, decomposition reaction is endothermic since the heat from the surrounding is used to break the bonds of the larger molecule.

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


(a) Thermal decomposition reaction: (Also known as Thermolysis)

Decomposition of Calcium Carbonate(CaCO3): When heated strongly, Calcium Carbonate decomposes into Calcium oxide and Carbon dioxide. This reaction is used for the preparation of Carbon dioxide.

CaCO3(s) ⎯ → CaO(s) + CO2(g)

(b) Electrolytic decomposition reaction:- (also known as Electrolysis)

Decomposition of water (Di-Hydrogen Oxide) : On passing electricity through liquid water, it decomposes into Hydrogen and Oxygen.

H2O—-> H2(gas) + O2(gas)

(c) Photo decomposition reaction (Also known as Photolysis)

Decomposition of Silver chloride (Agcl): In the presence of light Silver Chloride decomposes into Silver and Chloride.

2AgCl(s) ⎯⎯⎯⎯ 2Ag(s) + Cl2(g)

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


Displacement reaction is a type of reaction in which the highly reactive element displaces the less reactive element from its position and forms a new compound.

Also in displacement reaction single displacement reaction Takes place.

Double Displacement Reaction: This is a type of reaction in which both the Elements displaces each Other.


NCERT Solutions for Class 10 Science Chapter 1 (Chemical Reactions and Equation) 9


Displacement reaction


Double displacement reaction


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


2AgNO3 (aq) + Cu (s) → Cu(NO3)2 (aq) + 2Ag (s)
Silver Nitrate + Copper → Copper Nitrate + Silver

In this Cu displaces Ag from Silver nitrate and forms Copper Nitrate {Cu(no3)2}

15. In the refining of Ag, The recovery of Ag from AgNO3 solution involves displacement reaction by Cu metal. Write down the reaction involved?



Yes, It involves the Displacement Reaction.

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


Precipitation Reaction is a type of reaction in which two soluble salts combine (in aqueous solution )with each other to form one Insoluble Substance. Ex:- AgNO3(aqueous) + KCl(aqueous) —–AgCl(precipitate) + KNO3(aqueous)

16. Explain the following in terms of gain or loss of oxygen with two examples each.
(a) Oxidation
(b) Reduction


Oxidation:- Gain of Oxygen, Loss of hydrogen. (When any element gains Oxygen or Losses hydrogen known as oxidation.)

Reduction:- Gain of Hydrogen. ( When an Element gain Hydrogen or loses Oxygen, This is called Reduction.)

17. A shiny brown colored element ‘X’ on heating in the air becomes black in color.
Name the element ‘X’ and the black colored compound formed.


Element ‘X’ is copper here.

Shiny Brown colored substance is Copper (Cu) and When a Metal(Copper) Reacts with Oxygen, it forms Metallic Oxides or Metal Oxides.

Metal + Oxygen -> Metal Oxides. So, Cu ( Copper ) + O2 ( Oxygen ) –> CuO ( Copper Oxide)

Here CuO i.e, Copper Oxide (CuO) Formed is Black in Colour. Copper Oxide is the Black Coloured Compound formed in the above Reaction.

18. Why do we apply paint on iron articles?


Iron articles are painted to prevent(Protect) them from rusting/Corrosion. After painting iron surface does not come in direct contact with moisture and air which causes Rusting/Corrosion.

Rusting Vs Corrosion. (Rusting is a Part of Corrosion. Rusting is a Special case when the Iron came to direct contact with the Oxygen or Moisture).

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


The main purpose of flushed the items that contain Oil and Fat is to save them from Rancidity. Nitrogen is a Very less reactive gas in nature and it didn’t react with the oil and fat Present in the food whereas, Oxygen does so that’s why we flushed the food containing Oil and Fat.

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


Rancidity is a Process in which the oil and fat-containing food react with Oxygen and as a result, it produces unpleasant taste and smell. The rancidity can be controlled by keeping the Food inside the Refrigerator or just by Nitrogen Flushing.

Corrosion is a natural process, which converts a refined metal to a more chemically-stable form, such as its hydroxides, oxides, or sulfides. It is the gradual destruction of metals. This process takes place when Material/Metal came in Direct contact with the Oxygen and the Moisture present in the Atmosphere.

NCERT Solutions for Class 10 Science Chapter 1:- These were some NCERT questions Answer. Hope you find your answer. If you have any doubts regarding this chapter then don’t forget to comment. I will try to reply to your answer as soon as possible for me.

What to do next after the NCERT Question/Answers of chapter 1. (NCERT Solutions for Class 10 Science Chapter 1)

Now if you have already completed the Notes of this chapter. Then well it’s awesome. But If you don’t have the notes of this chapter then you can read from here.

After Notes——> Go for the Extra questions of this chapter. Click here to read and also download the Practise questions form this link.

Note:- If you’re studying this chapter after your first semester then you need to do one more thing. To complete this chapter, concept and all topics. Do a study of the Exemplar problems of this chapter.

Notes, Practice Questions and Quiz Provided by my website are really very helpful and unique. So don’t forget to check them. Definitely all the Study Materials present on this website are sufficient to clear your all concepts and Doubts. Everything Present on this website is fully free for Everybody.

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