NCERT Solutions Class 10 Science Chapter 1

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

NCERT Solutions Class 10 Science Chapter 1 is a useful study material prepared by subject matter experts which has answers to all NCERT Class 10 Science book questions and are designed to clarify all your doubts by explaining every answer in an interesting way. The language used in NCERT Solutions for Class 10 Science Chapter 1 can be understood easily by all the students

NCERT Solutions for Class 10 Science Chapter 1 – A Brief Overview

NCERT Class 10 Science Chapter 1 mainly talks about chemical equations and how to balance them. With this, the students can also learn how certain chemicals react with others to create a completely new chemical. What makes this chapter interesting is the fact that the chemical equations and examples given are relatable. It mostly covers equations about chemicals that students widely use in their day-to-day life. For instance, every day students witness different chemical reactions like ice freezing, wax melting, salt dissolving in water, a candle’s flame extinguishing when someone blows it, rusting of iron, etc. All these instances are actually two or more chemicals reacting with each other and resulting in a change in their original properties. These reactions are usually irreversible. NCERT for Class 10 Science Chapter 1 covers all these reactions in detail.

The NCERT book has practice questions at the end of Chapter 1 so that students can revise the concepts learned and apply them in deriving the answers. To help students solve the practice questions, Extramarks provides NCERT Solutions for Class 10 Science Chapter Here are the benefits of referring to the solutions:

  • NCERT Solutions for Class 10 Science Chapter 1 are prepared by subject matter experts as per the latest CBSE guidelines.
  • NCERT Solutions Class 10 Science Chapter 1 can be accessed in both offline & online modes.
  • NCERT Solutions have simple language and answers are written in a step-by-step manner.

NCERT Solutions for Class 10 Science

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 Periodic Classification of Elements
Chapter 6 Life Processes
Chapter 7 Control and Coordination
Chapter 8 How do Organisms Reproduce?
Chapter 9 Heredity and Evolution
Chapter 10 Light Reflection and Refraction
Chapter 11 Human Eye and Colourful World
Chapter 12 Electricity
Chapter 13 Magnetic Effects of Electric Current
Chapter 14 Sources of Energy
Chapter 15 Our Environment
Chapter 16

Chemical Reactions

A chemical reaction is when one substance reacts with another substance to form a new compound chemical or substance. The substances that go through a chemical change in the reaction are called reactants whereas the new substance formed during the reaction is known as a product.  This new product has completely different properties in comparison to the reactants. A chemical equation is demonstrated by symbols. These symbols are a shorthand form of chemical names. For example:

H2S + O2 → H2O + SO2

When hydrogen sulfide reacts with oxygen molecules, it becomes water & sulfur dioxide.

In case of any chemical reaction, either or all of the below-listed changes in properties can be observed:

  • Change in the state
  • Change in color
  • Change in temperature 
  • Formation of gas

Types of Chemical Reactions

Depending on the type of above-stated changes that take place during a chemical reaction, they can be classified as:

Combination Reaction:

When there is a breaking and making of bonds between atoms, new substances are formed. This type of reaction is called a combination reaction.

H2 + Cl → 2HCl

Hydrogen reacts with chlorine to form hydrogen chloride compounds.

Decomposition Reaction:

A decomposition reaction is when a single reactant breaks down to form different substances. These substances can be two or more. Depending on the energy required for the decomposition reaction, it can be classified into:

–        Thermal Decomposition:

In a typical thermal decomposition reaction, heat energy is used for decomposing the reactant.

CaCO3 + Energy → CaO + CO2

Calcium carbonate when subjected to heat turns into oxo calcium and carbon dioxide.

–        Electrolysis:

Chemical reactions where electrical energy is used for the decomposition of the reactant is called electrolysis. For instance,

2NaCl → 2Na + Cl2

When electricity is passed through sodium chloride, in the presence of electric energy it decomposes into sodium and chloride.

–        Photochemical Reaction:

Chemical reactions where light energy is used for breaking down the reactant is called photolysis or photochemical reaction. For instance,

2AgCI(s) →2Ag(s) +CI2(g)

Silver chloride when subjected to light energy in the form of sunlight decomposes into silver metal and chlorine gas.

Exothermic or Endothermic Reaction:

Certain chemical reactions either liberate heat or absorb heat during the process. Depending on that, such decomposition reactions can be classified into exothermic or endothermic reactions.

–        Exothermic Reaction:

The type of chemical reaction in which the products are formed because of the liberation of heat is called exothermic or combustion reaction. When we breathe in oxygen and exhale carbon dioxide, it is called an exothermic reaction. Likewise, when vegetables and fruits compost, the reaction is called exothermic.

–        Endothermic Reaction:

The reactions that occur because of the absorption of heat, light or electricity are called endothermic reactions. All endothermic reactions require some form of energy for breaking down of the reactants For instance, photosynthesis is a type of endothermic reaction that occurs due to the presence of sunlight.

6CO2 (aq) + 12H2O (l) →  C6H12O6 + 6O2 + 6H2

Displacement Reaction:

When in a chemical reaction, a less reactive element gets replaced by a more reactive element from its compound, it is called a displacement reaction. Displacement reaction is also of two types:

–        Single Displacement Reaction:

In this type of chemical reaction, an element from the compound displaces another element from the same compound. For instance,

Mg + 2HCl → MgCl2 + H2

–        Double Displacement Reaction:

The type of displacement reaction in which groups of atoms in the molecules of a reactant are equally reactive and displace each other is called a double displacement reaction. As in this reaction, a precipitate is also produced, double displacement reactions are alternatively called as precipitation reactions. For example,

2KBr + BaI2 → 2KI + BaBr2

Oxidation & Reduction Reactions  Or Redox Reactions :

In this type of chemical reaction, oxygen is either added or removed from the substance. If during the reaction, the substance gains oxygen, it is said to be oxidised. Whereas  if during the reaction, the substance loses oxygen, it is said to be a reduction reaction.

The substance that oxidises another substance is called the oxidising agent. While the substance that causes the other substance to lose oxygen is called the reduction agent.

In simpler words, when both oxidation and reduction occur simultaneously, such reactions are called oxidation & reduction reactions or redox reactions. 

MnO2 (s) + 4HCl→ MnCl2 (aq) + Cl2 (g) + 2H2O

In the above-stated example, HCl oxidizes to Cl2. On the other hand, MnO2 reduces to MnCl2.


Have you ever seen some metals like iron get coated by reddish brown powder?  This happens when the upper surface of iron comes in contact with air, water, and chemicals in the atmosphere which leads to its rusting. This process is known as Corrosion. Some other examples of corrosion are black and green coating on silver and copper, respectively.  It is a redox reaction and can be prevented by painting, galvanizing or electroplating the iron surface.


When fats and oil are oxidized leading to a loss in their original taste or smell. This is called rancidity. For instance, extra virgin olive oil goes rancid with time or when heated above its boiling point. But rancidity can be easily prevented by:

  • Keep items in airtight containers.
  • For cooked items that are prone to rancidity, refrigerate them. Alternatively, you can also pack them in nitrogen gas.
  • Avoid keeping rancidity-prone foods under direct sunlight.
  • Add BHA or BHT in the items to avoid rancidity.

Related Questions

Write the balanced equation for the following chemical reactions.

  1. i) Hydrogen + Chlorine →→ Hydrogen chloride

Ans: The balanced equation for the given reaction is: H2(g)+Cl2(g)→2HCl(g)

(A balanced equation should have the same number of atoms on both the reactant and product side of the equation.)

Q.1 When sodium sulphate solution is treated with barium chloride solution, a white precipitate is formed. Name the reaction and also write the balanced chemical reaction.

Ans- The reaction involves the exchange of ions between two compounds to form two new compounds and thus it is a double displacement reaction. The balanced chemical equation for the given reaction can be written as follows:

Na2SO4(aq)+BaCl2(aq) BaSO4( s)+2NaCl(aq)

Q.2 In the following reaction, identify the species that undergoes –


(i) Oxidation
(ii) Reduction
Give reasons also.


Fe(s)2e Fe2+(aq)

Here, iron loses its two electrons to form Fe2+ ions. As we know that oxidation is the loss of electron(s), so iron undergoes oxidation.

Ni2+(aq)+2e Ni(s)

Here, Ni2+ ions gain two electrons to form nickel. As we know that reduction is gain of electron(s), so nickel undergoes reduction.

Q.3 Differentiate between combination reaction and decomposition reaction. Give one example of each of these reactions.


Combination reaction Decomposition reaction
A reaction in which two or more substances combine to give a single substance is known as combination reaction.

A reaction in which a compound is broken into two or more simpler substances is known as decomposition reaction.















Q.4 Write a balanced chemical reaction for each of the following reactions:
(a) Carbon dioxide is passed through lime water.
(b) A strip of copper metal is dipped in the solution of silver nitrate solution.

Ans- (a) When carbon dioxide gas is passed through lime water, the lime water turns milky due to the formation of white precipitate of calcium carbonate.


(b) When a strip of copper metal is dipped in the solution of silver nitrate solution, a greyish white deposit of silver metal is deposited on the strip.


Q.5 (a) Respiration is considered an exothermic reaction. Why?
(b) Write an example of exothermic reaction.

Ans- (a) During respiration, food is oxidised and energy is released. Therefore, it is considered an exothermic reaction.
(b) Reaction of quick lime with water is an exothermic reaction.


Q.6 How a double displacement reaction is different from simple displacement reaction? Explain with the help of an example.

Ans– In a double displacement reaction, exchange of ions takes place among the reactants, while in displacement reaction more reactive metal displaces less reactive metal from its salt.

Example of displacement reaction:


Here, Fe displaces Cu from CuSO4 because Fe is more reactive than Cu.

Example of double displacement reaction:


Here, the exchange of ions between reactants takes place.

Q.7 Explain the term combination reaction with the help of an example.

Ans- When two reactants combine to form a single product, the reaction is called combination reaction.

2H2(g)+O2(g) →2H2O(g)

Q.8 Write balanced chemical reactions which represent the following:
(a) Ferrous sulphate is heated.
(b) Hydrogen gas combines with nitrogen to form ammonia.
(c) Magnesium metal reacts with water to give magnesium hydroxide and hydrogen.

Ans- (a)2FeSO4Heat Fe2O3+SO2+SO3 (b) N2+3H22NH3 (c) Mg+2H2O  Mg(OH)2+H2

Q.9 Write the name of the chemical and its reaction which is used in black and white photography.

Ans- Silver bromide is used in black and white photography. When exposed to sunlight, it decomposes to form silver and bromine.


Q.10 Give two examples of redox reactions.

Ans- (a) ZnO+C  Zn+CO(b) MnO2+4HCl  MnCl2+2H2O+Cl2

Q.11 Write any four observations that help us to determine whether a chemical reaction is taking place.


(a) Change in state
(b) Change in colour
(c) Evolution of a gas
(d) Change in tempreature

Q.12 Balance the following chemical equations:

(a) Na+O2 Na2O (b) NaCl+H2O  NaOH+Cl2+H2 (c) NH42CO32NH3+H2O+CO2


(a) 4Na(s)+O2 (g)2 Na2O(s) (b) 2NaCl(aq)+H2O(l)  NaOH(aq)+Cl2(g)+H2(g) (c) NH42CO3(s) 2NH3(g)+H2O(g)+CO2(g)

Q.13 Na2SO4 (aq) +BaCl2(aq) 2 NaCl (s) + BaSO4 (aq)

Is this reaction an example of precipitation reaction? Also give reason for your answer.

Ans- When sodium sulphate is mixed with barium chloride, white cloured barium sulphate is formed which is insoluble in water. The insoluble substance is called precipitate and this reacion is called precipitation reaction.

Q.14 Identify the substance which is oxidised and which is reduced in the following reaction:


Ans- In this reaction, ZnO is reduced to Zn and C is oxidised to CO.

Q.15 Represent the following by balanced chemical equations:
(a) Iron nail is kept in a copper sulphate solution.
(b) Silver chloride is kept in sunlight.
(c) Ferrous sulphate is heated at room temperature.
(d) Silver nitrate reacts with hydrochloric acid.
(e) Methane burns in presence of air.


(a) Fe(s)+CuSO4 (aq) FeSO4(aq)+Cu(s)

(b) 2AgCl(s) Sunlight2Ag(s)+Cl2(g)

(c) 2FeSO4(s)Heat Fe2O3(s)+SO2(g)+SO3(g)

(d) AgNO3(aq)+HCl (aq) AgCl(s)+HNO3(aq)

(e) CH4(g)+2O2(g)  CO2(g)+2H2O(g)

Q.16 Balance the following chemical equations:

(a) HNO3+Ca(OH)2CaNO32+H2O (b) NaOH+H2SO4Na2SO4+H2O (c) NaCl+AgNO3AgCl+NaNO3 (d) BaCl2+H2SO4BaSO4+HCl (e) PbNO32Δ PbO+NO2+O2

Ans- (a) 2HNO3+Ca(OH)2CaNO32+2H2O(b) 2NaOH+H2SO4Na2SO4+2H2O(c) The equation is already balanced.(d) BaCl2+H2SO4BaSO4+2HCl(e) 2 PbNO32Δ2PbO+4NO2+O2

Q.17 Write one difference between :
(a) Oxidation and reduction reactions
(b) Exothermic and endothermic reactions


Oxidation reaction Reduction reaction
Addition of oxygen or removal of hydrogen Addition of hydrogen or removal of oxygen





Exothermic reaction Endothermic reaction
A reaction which involves evolution of heat. A reaction which involves absorption of heat.




Q.18 Write the chemical equation and its type for each of the following:
(a) Silver chloride is exposed to sunlight.
(b) Manganese dioxide reacts with hydrochloric acid.
(c) Zinc rod is dipped in copper sulphate solution.
(d) Solution of sodium sulphate and barium chloride are mixed.
(e) Calcium carbonate is heated.


(a) It is decomposition reaction.

2AgCl(s)Sunlight2Ag(s)+Cl2( g)

(b) It is oxidation reaction.

MnO2(s)+4HCl(aq)  MnCl2(aq)+2H2O(l)+Cl2(g)

(c) It is displacement reaction.

Zn(s)+CuSO4(aq)  ZnSO4(aq)+Cu(s)

(d) It is double displacement reaction.

Na2SO4(aq)+BaCl2(aq) BaSO4( s)+2NaCl(aq)

(e) It is decomposition reaction.

CaCO3( s)HeatCaO(s)+CO2( g)

Q.19 When a compound of lead is heated, brown coloured fumes evolve from it.
(i) Name the compound.
(ii) Write the balanced chemical equation.
(iii) Write the chemical name of brown coloured fumes.
(iv) Name the type of reaction.
(v) Is this reaction exothermic or endothermic?


(i) The compound is lead nitrate.

(ii) 2 PbNO322PbO+4NO2+O2

(iii) Nitrogen dioxide
(iv) Decomposition reaction
(v) Endothermic reaction


(i) Name this reaction.
(ii) Name the more reactive element.


(i) The given reaction is an example of displacement reaction.
(ii) Element B is more reactive because it displaces element A from its salt.

Q.21 Name the type of following reactions:

(a) Na2SO4+BaCl2 BaSO4+2NaCl (b) Pb+CuCl2 PbCl2+Cu (c) MnO2+4HCl  MnCl2+2H2O+Cl2 (d) CaO+H2O Ca(OH)2 (e) 2 PbNO322PbO+4NO2+O2

Ans- (a) Double displacement reaction
(b) Displacement reaction
(c) Redox reaction
(d) Combination reaction
(e) Decomposition reaction

Q.22 What are exothermic and endothermic reactions? Give two examples for each.

Ans- Exothermic reactions: The reactions in which heat is evolved along with the products are known as exothermic reactions.

For example,
(1) Burning of natural gas:

CH4( g)+2O2( g)CO2( g)+2H2O(g)+ Heat

(2) Formation of Ammonia in presence of Ni:


Endothermic reactions: The reactions in which heat is absorbed are known as endothermic reactions.

For example,
(1) Formation of carbon disulphide:

CCarbon+SSulphur HeatCS2Carbon disulphide

(2) Formation of nitric oxide:

N2Nitrogen+O2OxygenHeat2NONitric oxide

Q.23 Write one example of each of the following type of reaction:
(a) Double displacement reaction
(b) Redox reaction
(c) Decomposition reaction
(d) Combination reaction
(e) Displacement reaction

Ans- (a) Na2SO4(aq)+BaCl2 (aq) BaSO4(s)+2NaCl(aq) (b) MnO2(s)+4HCl (aq) MnCl2(aq)+2H2O(l)+Cl2(g) (c) 2 PbNO32 (s)2PbO(s)+4NO2(g)+O2(g) (d) CaO(s)+H2O(l) Ca(OH)2(aq) (e) Pb(s)+CuCl2(aq)  PbCl2(aq)+Cu(s)

Q.24 Identify the substances that are oxidised and the substances that are reduced in the following reactions:
(a) Fe + CuSO4 FeSO4 + Cu
(b) Fe2O3 +2Al Al2O3 +2Fe
(c) MnO2 + 4HCl MnCl2 + 2H2O +Cl2

Ans- (a) Fe – Oxidised
Cu – Reduced
(b) Fe2O3 – Reduced
Al – Oxidised
(c) MnO2 – Reduced
HCl – Oxidised

Q.25 In the following reaction between lead sulphide and hydrogen peroxide:
PbS(s) + 4H2O2(aq) → PbSO4(s) + 4H2O

(a) Which substance is reduced?
(b) Which substance is oxidised?


(a) H2O2
(b) PbS

Q.26 Write the term used for the symbolic representation of a reaction.

Ans- Chemical equation

Q.27 Why do we apply paint on iron articles?

Ans- We paint iron articles to protection them from rust.

Q.28 Define the term corrosion.

Ans- Corrosion is defined as the process of slow and gradual conversion of a metal into its oxide, sulphide or sulphate by the attack of air and water present in the atmosphere. Rusting of iron is an example of corrosion.

Q.29 Define the term reduction.

Ans- Reduction is defined as
(i) the addition of hydrogen or electropositive element to a compound or
(ii) the removal of oxygen or electronegative element from a compound
Examples :

(i) 2Na(s) + H2(g) → 2NaH(s) (ii) CuO(s) + H2(g) → Cu(s) + H2O(g)

Q.30 What are combination reactions?

Ans- Reactions in which two or more substances combine to form a single substance, are called combination reactions.


(a) 2Mg(s)+O2(g) 2MgO(s)(b) 2Na(s)+Cl2(g) 2NaCl(s)

Q.31 What are double displacement reactions? Give an example.

Ans- Double displacement is a reaction in which compounds exchange their ions, i.e. two atoms or ions displace each other.

BaNO32(aq)Barium nitrate+NH42CO3(aq)Ammonium carbonateBaCO3Barium carbonate+ 2NH4NO3(aq)Ammonium nitrate

Q.32 Why does the colour of copper sulphate solution change when an iron nail is dipped in it?

Ans- Iron displaces copper from copper sulphate solution and form iron sulphate solution. The colour of iron sulphate solution is green.

Q.33 What type of reaction is represented by the digestion of food in our body?

Ans- Decomposition reaction

C6H12O6(aq) + 6O2(aq)6CO2(aq)+6H2O(l)+Energy

Q.34 Define rancidity.

Ans- The condition produced by aerial oxidation of fats and oils in foods marked by unpleasant smell, taste and makes food unfit for eating is called rancidity.

Q.35 What is a chemical reaction?

Ans- A chemical reaction is defined as the overall change in the energy of the system and the generation of new products by breaking and formation of chemical bonds of reactants.

Q.36What is meant by oxidation?

Ans- Oxidation is defined as (i) the addition of oxygen or electronegative atom to an element or compound (ii) the removal of hydrogen or electropositive atom from a compound.

Q.37 What are displacement reactions?

Ans- The reactions in which more reactive element displaces less reactive element from its salt solution are called displacement reactions.

              2KI (aq)  +  Cl2 (g)    →  2KCl (aq)  +  I2(g)

Q.38 What is catalytic decomposition?

Ans- The reactions in which a compound splits up into two or more simpler substances in the presence of catalyst are called catalytic decomposition reactions. Example:- Digestion of food in human body

Q.39 Which of the following is a combination and which is a displacement reaction?                 

(a)      Cl2   +   2KI   →    2KCl   +   I2

(b)      2K   +   Cl   →   2KCl     


(a) Displacement reaction
(b) Combination reaction

Q.40 Define oxidising agent.

Ans- The substance which gives oxygen for oxidation or removes hydrogen is called an oxidising agent.

Q.41 What do you understand by a balanced chemical equation? Why should the chemical equation be balanced?

Ans- A chemical equation which consists of an equal number of atoms of each element on both sides of the equation is known as balanced chemical equation.

The chemical equation should be balanced due to the following reasons:

(a)  The number of various types of atoms in reactants must be equal to the number of same type of atoms in products.

(b)  The total mass of all the reactants must be equal to the total mass of the product

So, the chemical equation is balanced to satisfy the law of conservation of mass in chemical reaction.

Q.42 Write the balanced equation for the following chemical reactions-

(a) Sodium + Water  Sodium hydroxide + Hydrogen(b) Barium chloride + Aluminium sulphate  Barium sulphate + Aluminium chloride(c) Hydrogen sulphide + Oxygen  Water + Sulphur dioxide


(a) 2Na(s)+2H2O(l) 2NaOH(aq)+H2(g)(b) 3BaCl2(aq)+Al2SO43(aq)3BaSO4(s)+2AlCl3(aq)(c) 2H2 S(g)+3O2 (g)2H2O(l)+2SO2(g)

Q.43 A solution of a substance ‘X’ is used for white washing.
(a) Name the substance ‘X’ and write its formula.
(b) Write the reaction of the substance ‘X’ named in (a) above with water.


(a) The substance ‘X’ is calcium oxide and its formula is CaO.

(b) CaO (s)(Calcium oxide) + H2O(l)(Water)Ca(OH)2(aq)(Calcium hydroxide)   Or (Slaked lime)

Q.44 Why should magnesium ribbon be cleaned before burning in air?

Ans- Magnesium ribbon should be cleaned before burning in air due to the presence of a thin layer of oxide on the surface of magnesium at ordinary temperature. This layer prevents magnesium from further oxidation.

Q.45 (i) What is respiration?
(ii) Is respiration exothermic reaction or endothermic? Explain with reason.


(i) Respiration is a metabolic process in which the food consumed is broken down into smaller and simpler complexes through chemical reaction with oxygen and results in the release of energy to carry out life processes and other activities.

C6H12O6(aq)Glucose+6O2( g)6CO2( g)+6H2O(l)+ energy 

(ii) Since energy is released during the process, respiration is considered as an exothermic reaction.

Q.46 What is the difference between combination and decomposition reaction? Give one example of each type.


Combination reaction Decomposition reaction
The reaction in which two or more substances (elements or compounds) combine to form a new single product is known as combination reaction. he reaction in which a single substance decomposes to give two or more substances is known as decomposition reaction.
For example:

For example:









Decomposition reactions are opposite to combination reactions.

Q.47 Write two uses of decomposition reactions.


1.These reactions are used to extract several metals from their oxides or other salts. When the oxide or salt is electrolysed, metal is obtained. For example, aluminium metal is obtained by passing electricity in molten aluminium oxide.

2. Digestion of food in our body is also an example of decomposition reaction. The starch (carbohydrates) present in food is decomposed to give simple sugar (glucose) and the proteins are broken down into amino acids.

Q.48 What is the difference between displacement and double displacement reactions? Write example of each reaction.


Displacement reaction Double displacement reaction
The reaction in which one element displaces another element from its compound is known as displacement reaction. In these reactions, more reactive element displaces less reactive element from its compound. The reaction in which two different atoms or group of atoms (ions) are displaced by other atoms or group of atoms (ions) is known as double displacement reaction.

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

In the above reaction, silver is replaced by copper because copper is more reactive than silver.


Na2SO4(aq) + BaCl2(aq) BaSO4(s) + 2NaCl(aq)Sodium sulphate Barium chloride Barium sulphate Sodium chloride

In the above reaction,




ions and


ions displace


ions or both ions exchange each other. These reactions occur in ionic compounds.





























Q.49 What is observed when a solution of potassium iodide is added to a solution of lead nitrate taken in a test tube? What type of reaction is this? Write a balanced chemical equation to represent the above reaction.

Ans- When a solution of potassium iodide (KI) is added to a solution of lead nitrate [Pb(NO3)2], then a yellow precipitate of lead iodide (PbI2) is formed. This is a double displacement reaction.

PbNO32(aq)Lead nitrate+2KI(aq)Potassium iodidePbI2( s)Lead iodide(yellow ppt.)+2KNO3(aq) Potassium nitrate

Q.50 Write the type of chemical reaction represented by the following equations

(i) 2Al(s)+6HCl(ag)2AlCl3(aq)+3H2( g)

(ii) 2KBr(aq)+Cl2( g)2KCl(g)+Br2( g)

(iii) 2Zn(s)+O2( g)2ZnO(s)


(i) Redox reaction
(ii) Displacement reaction
(iii) Combination reaction

Q.51 What happens when an iron nail is dipped in copper sulphate solution?

Ans- When an iron nail is dipped in copper sulphate solution, the blue colour of copper sulphate changes to light green due to the formation of ferrous sulphate and copper is formed. This happens because iron is more reactive than copper, so, it displaces copper from its salt solution.

Fe(s)Iron+CuSO4(ag)Blue SolutionFeSO4(ag)Light Green+Cu(s)Copper

Q.52 Explain the terms oxidising and reducing agents with an example of each.

Ans- Oxidising agent: The substance, which oxidises elements or compounds, is known as an oxidising agent.
For example:

4Fe(s)+3O2(g) 2Fe2O3(s)

Hence, oxygen is an oxidising agent. It oxidises iron (Fe3+ ion) to ferric oxide (Fe2O3 ).

Reducing agent: The substance which reduces an element or a compound is known as reducing agent.
For example:

SnCl2(aq)+2FeCl3 (aq) SnCl4(aq)+2FeCl2(aq)

Stannous chloride is a reducing agent. It reduces ferric chloride (or Fe3+ ion) to ferrous chloride (or Fe2+).

Q.53 Packets of potato chips are filled with a gas. Name this gas and explain its use.>

Ans- Packets of potato chips are filled with nitrogen gas. Oil and fat containing food items are flushed with nitrogen to prevent them from being oxidised. They become rancid and their smell and taste change.

Q.54 Translate the following statements into chemical equations and then balance them.
(a) Sodium chloride with sulphuric acid giving sodium sulphate and hydrochloric acid
(b) Zinc reacting with silver chloride to give zinc chloride and silver


(a) 2NaCl(aq)+H2SO4(aq)  Na2SO4(aq)+2HCl(aq)

(b) 2Zn(s)+AgCl2(aq) 2ZnCl2(aq)+Ag(s)

Q.55 What do you understand by corrosion? Give an example.

Ans- The process of slow and gradual conversion of a metal into their compounds by the attack of air and water present in atmosphere is known as corrosion. Corrosion, in case of iron is called rusting. Rust is hydrated iron (III) oxide [Fe2O3 .H2O]. The presence of oxygen and water (moisture) is essential for rusting to take place.

Q.56 Identify the component oxidised in the following reaction:
H2S + Cl2 S + 2HCl

Ans- H2S

In the given reaction, hydrogen sulphide is oxidised to sulphur by the removal of hydrogen and chlorine is reduced to hydrogen chloride by the addition of hydrogen.

Please register to view this section

FAQs (Frequently Asked Questions)

1. What are the topics covered in NCERT Solutions for Class 10 science Chapter 1?

The topics covered in the NCERT Solutions for Class 10 Science Chapter 1 by Extramarks are –

1.1 – Chemical Equations

1.1.1 – Writing a Chemical Equation

1.1.2 – Balanced Chemical Equations

1.2 – Types of Chemical Reactions

1.2.1 – Combination Reaction

1.2.2 – Decomposition Reaction

1.2.3 – Displacement Reaction

1.2.4 – Double Displacement Reaction

1.3 – Have you observed the effects of oxidation reactions in everyday life?

1.3.1 – Corrosion

1.3.2 – Rancidity

2. What are the key benefits of NCERT Solutions for Class 10 Science Chapter 1 by Extramarks?

  •  NCERT Solutions for Class 10 Science Chapter 1 by Extramarks is available both online and offline.
  •   With the help of well explained solutions of the textbook problems given in NCERT Class 10 science Chapter 1,  students can become perfect at solving and balancing chemical equations. This gives students the confidence to solve even the trickiest questions in CBSE Class 10 Science Board Exam with ease.
  •       Class 10 science Chapter 1 NCERT Solutions are self-explanatory and prepared by experts in a simple language. So, students can prepare from the solved NCERT questions and learn to frame accurate answers for their exams.