NCERT Solutions for Class 10 Science Chapter 1 Chemical Reactions and Equations  


NCERT Solutions for Class 10 Science Chapter 1 Chemical Reactions and Equations covers all the main topics in detail, allowing students to grasp the ideas more easily. Class 10 NCERT solutions science chapter 1 lays the foundation of chemistry.

Students can also find an explanation of NCERT solutions for class 10 science chapter 1along with exercise question answers.

Table of Contents

NCERT Solutions for Chemical Reactions and Equations Class 10 Chapter

Class 10 NCERT solutions science chapter 1primarily concerned with the writing of chemical equations, as well as the writing and balancing of chemical equations. Students also learn the fundamentals of chemical reactions, their types, and the implications of a chemical oxidation reaction in our daily lives in this chapter.   

The NCERT Solutions Class 10 Science Chapter 1 provides an overview of the chapter’s core themes and assists you in becoming familiar with important subjects such as writing and balancing chemical equations.  

NCERT Solutions for Class 10 Science Chapter 1 Exercise Question Answer 

 1. Which of the statements about the reaction below are 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  

Ans: The answer to the question is i) (a) and (b)

Explanation: a) because oxygen is being removed, not lead is getting reduced, and b) because the removed oxygen from Lead is added to the elemental carbon.  

Also Read: Tyndall Effect Class 10 Notes with Example

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.  

Ans: The answer to the above question is option IV) Displacement reaction.  

Explanation: Aluminum Oxide is formed when the oxygen from the ferrous oxide is displaced with the aluminum metal. Aluminum is a more reactive metal than Fe in this reaction. As a result, Al will displace Fe from its oxide. The displacement reaction is a sort of chemical reaction in which one element displaces another. More reactive metal is displacing less reactive metal in this case. Because of the onetime displacement, the reaction is referred to as a single displacement reaction.  

3. What happens when dilute hydrochloric acid is added to iron filings? 

I) Hydrogen gas and iron chloride are produced.  

II) Chlorine gas and iron hydroxide are produced.  

III) No reaction takes place.  

IV)Iron salt and water are produced.  

Ans: The answer to the above question is I) Hydrogen gas and iron chloride are produced.  

Explanation: The iron fillings displace the chlorine from hydrogen chloride, resulting in the process below. 

2HCl + Fe → FeCl+ H2 

4. What is a balanced chemical equation? Why should a chemical equation be balanced?  

Ans: A chemical reaction where the number of different atoms of all the elements on both the reactant and the product sides is equal is called a balanced chemical equation.  

Chemical equations must be balanced since mass cannot be generated or destroyed, according to the law of conservation of mass. As a result, the total mass of reactants should match the total mass of products in a chemical reaction. As a result, the total mass of reactants equals the total mass of products in a balanced chemical equation.  

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

I) Hydrogen gas combines with nitrogen to form ammonia.

II) Hydrogen sulphide gas burns in the air to give water and Sulphur dioxide.

III) Barium chloride reacts with aluminum sulphate to give aluminum chloride and a precipitate of barium sulphate

IV) Potassium metal reacts with water to give potassium hydroxide and hydrogen gas. 


I) 3H2+N2→2NH3  

II) 2H2S + 3O→ 2H2O + 2SO2

III) 3BaCl+ Al2(SO4)→ 2AlCl+ 3BaSO4 

IV) 2K + 2H2O → 2KOH + H2 

6. Balance the following chemical equations.  

I) HNO3 + Ca (OH)2 → Ca (NO3)2 + H2O

II) NaOH + H2SO4 → Na2SO4 + H2O

III) NaCl + AgNO3 → AgCl + NaNO3

IV) BaCl2 + H2SO4 → BaSO4 + HCl


I) HNO+ Ca(OH)→ Ca (NO3)+ 2H2

II) 2NaOH + H2SO→ Na2SO+ 2H2O

III) NaCl + AgNO→ AgCl + NaNO3 

IV) BaCl+ H2SO→ BaSO+ 2HCl 

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

I) Calcium hydroxide + Carbon dioxide — > Calcium carbonate + Water 

II) Zinc + Silver nitrate — > Zinc nitrate + Silver 

III) Aluminum + Copper chloride —> Aluminum chloride + Copper 

IV) Barium chloride + Potassium sulphate —> Barium sulphate + Potassium chloride 


I) 2Ca(OH)+ 2CO→ 2CaCO+ 2H2O

II) Zn + 2AgNO→ Zn(NO3)+ 2Ag 

III) 2Al + 3CuCl→ 2AlCl+ 3Cu 

IV) BaCl+ K2SO→ BaSO+ 2KCl

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

I) KBr + BaI→ KI + BaBr2 

II) ZnCO→ ZnO + CO2 

III) H+ Cl → HCl 

IV) Mg + HCl → MgCl+ H2


I) 2KBr + BaI→ 2KI + BaBr2 

This is a Double Displacement Reaction 

II) ZnCO→ ZnO + CO2

This is a Decomposition Reaction

III) H2 + Cl → 2HCl 

This is a Combination Reaction 

IV) Mg + 2HCl → MgCl+ H2  

This is a Displacement Reaction 

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


The reaction in which energy is absorbed from the environment in the form of heat is called an endothermic reaction. Examples include photosynthesis, ice melting, and evaporation. Because in such a reaction, the reactants have less energy than the products, energy is absorbed to complete the reaction.  

The reaction in which energy is released from the system to the environment, along with the formation of other products, is called an exothermic reaction. For example, explosions, concrete settings, nuclear fission, and fusion.  

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

Ans: Energy is required for life to survive. This energy comes from the food we eat. The food molecules are broken down into simpler molecules, like glucose, during the digestive process. These molecules react with the oxygen in our cells to produce carbon dioxide and water, as well as a negligible amount of energy (Respiration process). Respiration is an exothermic reaction since the energy is in the form of heat (which keeps our body temperature constant). The reaction that takes place is: C6H12O+ 6O→ 6CO+ 6H2O + Energy.

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


The reaction between two or more molecules to generate a larger molecule is known as a combination reaction, whereas the decomposition reaction is described as the splitting of larger molecules into two or more smaller molecules. The decomposition reaction is the polar opposite of the combination reaction, as this illustrates. 

The decomposition reaction is almost always endothermic because heat from the environment or produced heat is required to dissolve the bonds of the bigger molecule. Examples of decomposition reactions are: 

ZnCO3 → ZnO + CO2

CaCO3 + Energy → CaO + CO2 

2HgO → 2Hg + O2

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

Ans: a) Thermal decomposition reaction (Thermolysis)  

Decomposition of potassium chlorate: Potassium chlorate decomposes into potassium chloride and oxygen when heated to a high temperature. The manufacture of oxygen is accomplished via this reaction.  

2KClO+ Heat → 2KCl + 3O2 

b) Electrolytic decomposition reaction (Electrolysis) 

 Decomposition of sodium chloride: It decomposes into sodium and chlorine when electricity is passed through molten sodium chloride.  


c) Photodecomposition reaction (Photolysis)  

Decomposition of hydrogen peroxide: Hydrogen peroxide decomposes into water and oxygen in the presence of light. 


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

Ans: A displacement reaction occurs when a more reactive substance displaces a less reactive substance from its salt solution, but a double displacement reaction occurs when two compounds exchange ions mutually.  

A displacement reaction involves only one displacement, whereas a double displacement reaction involves two displacements between the molecules, as the name suggests.  


Displacement reaction

Mg + 2HCl → MgCl+ H2 

Double displacement reaction  

2KBr + BaI2 → 2KI + BaBr2 

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

Ans: The equation involved in the recovery of silver from silver nitrate solution in silver refining is as follows: 

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

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


When two solutions containing soluble salts are mixed, the ions are exchanged between the compounds in a twofold displacement reaction. When one of these compounds solidifies (i.e. becomes insoluble in water), it descends to the bottom of the container. The precipitate is solid, while the precipitation reaction is the reaction in which it occurs.  

Some examples of precipitation reactions are:  

CdSO4(aq) + K2S(aq) → CdS(s) + K2SO4(aq)  

Na2CO3 (aq)+CaCl2 (aq)→CaCO3 (s)↓+2NaCl(aq) 

16. Explain the following in terms of gain of oxygen with two examples each.  

(a) Oxidation  

(b) Reduction  

Ans: (a) Oxidation is a reaction in which oxygen or an electronegative species is introduced to a substance or hydrogen or a positive species is removed from a substance.  

Example: 4Na(s) + O2(g) → 2Na2O(s)

H2S + O→ H2O + SO2 

(b) Reduction is a reaction that adds hydrogen or an electropositive species to a substance while removing oxygen or an electronegative species.  

Example: CuO(s) + H2(g) → Cu(s) + H2O(l) 

2HgO → 2Hg + O2 

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.  

Ans: Copper is a metal with a shiny brown color (Cu). When copper is heated in the air, it combines with oxygen in the air to generate copper oxide. As a result, copper oxide is a black-colored compound. 

2Cu(s) + O2(g) → 2CuO(s) 

18. Why do we apply paint on iron articles? 

Ans: Iron is a reactive metal. To prevent iron articles from rusting, they are painted. When the metal surface is left unpainted, it is exposed to atmospheric oxygen and, in the presence of moisture, it turns into Iron (III) oxide. However, if the surface is painted, it does not come into touch with moisture or air, avoiding rusting. 

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

Ans: Oils and fat-containing food products are perishable and can degrade if exposed to oxygen. This is because oil and fats are reactive and easily oxidized when exposed to oxygen. The primary goal of flushing nitrogen into food packages containing oil and fat items is to prevent rancidity, which occurs when the oil or fat combines with air, producing an undesirable odor and flavor. As a result, flushing nitrogen creates an unreactive environment, which prevents rancidity.

20. Explain the following terms with one example each.  

(a) Corrosion  

(b) Rancidity  

Ans: (a) Corrosion is a process that occurs when a refined metal is oxidized by atmospheric oxygen, resulting in the formation of oxides, which are more stable compounds. During the corrosion process, the metal steadily deteriorates. When iron rusts, it is transformed into iron oxide, which is a form of corrosion. Every year, millions of dollars are spent to keep bridges and other landmarks from rusting.   

(b) The process in which food items containing fats and oils are oxidized is called rancidity. The unpleasant taste and odor created by the aerial oxidation of the oil and fat present in the food substance are because of rancidity. When food is kept in the refrigerator, rancidity is delayed because the low temperature inhibits the oxidation reaction.  

We can avoid rancidity by putting the food items in air-tight containers, adding antioxidants like BHA, and adding nitrogen to food packets in order to prevent oxidation.