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

NCERT CBSE Board Solution for Class 10 Science Chapter 1 Chemical Reactions and Equations notes video and question-answer and chapter related all best resource.

Class 10 Science Chapter 1 Chemical Reactions and Equations

Class 10 Science Chapter 1 Important Notes Keeping Exams In Mind

1.  Chemical reactions- The transformation of chemical substance into a new chemical substance by making and breaking of bonds between different atoms is known as Chemical Reaction. { Class 10 Science Chapter 1 Notes }

2.  Signs of a chemical reaction- These factors denote that a chemical reaction has taken place- change of state of substance, change of color of substance, evolution of heat, absorption of heat, evolution of gas and evolution of light.

3.  Chemical Equation: The representation of chemical reaction by means of symbols of substances in the form of formulae is called chemical equation. E.g. – H2 + O2 ⇒ H2O

4.  Balanced Chemical Equation: A balanced chemical equation has number atoms of each element equal on both left and right sides of the reaction.

      *Note- According to Law of Conservation of Mass, mass can neither be created nor destroyed in a chemical reaction. To obey this law, the total mass of elements present in reactants must be equal to the total mass of elements present in products.

5.  Types of Chemical Reactions- {Class 10 Science Chapter 1 Mind Map}

                      I.  Combination- When two elements or one element and one compound or two compounds combines to give one single product.

                     II.  Decomposition- Splitting of a compound into two or more simple products.

                    III.  Displacement- It takes place when a more reactive metal displaces a less reactive metal.

                    IV.  Double displacement- Reactions in which ions are exchanged between two reactants forming new compounds are called double displacement reactions.

                     V.  Precipitation- The insoluble compound called precipitate forms in this reaction.

                    VI.  Exothermic- Reactions which produce energy are called exothermic reaction. Most of the decomposition reactions are exothermic.

                   VII.  Endothermic- Reactions which absorb energy are called endothermic reaction. Most of the combination reactions are endothermic.

                  VIII.  Oxidation: Gain of oxygen or removal of hydrogen or metallic element from a compound is known as oxidation.

                     IX.  Reduction: Addition of hydrogen or removal of oxygen from a compound is called reduction.

                       X.  Redox- A chemical reactions where oxidation and reduction both take place simultaneously are also known as redox reaction.

                             Eg – NaOH + HCl ⇒ NaCl + H2O

6.  Rusting- When iron reacts with oxygen and moisture forms a red substance called rust.

7.  Rancidity- Oils and fats when get oxidized on exposure to air show a change in taste and smell.

8.  Corrosion- Metals when attacked by oxygen, water, acids, gases, present in air changes its surface which is called corrosion.

Some Important Question for class 10 Science Chapter 1

  1. What is a redox reaction?
  2. What is corrosion? Explain its advantage and disadvantage.
  3. What is rancidity? How can we reduce the problem of rancidity?
  4. How is corrosion different from rusting?
  5. What is meant by endothermic and exothermic reactions? Give suitable example for each.
  6. Define different types of chemical reaction and give examples for each.
  7. Why is photosynthesis considered as an endothermic reaction?
  8. In electrolysis of water, why is the volume of gas collected over one electrode double that of the other electrode?
  9. What happens when water is added to solid calcium oxide taken in a container? Write a chemical formula for the same.
  10. Give one use of quick lime.
  11. Give three types of decomposition reaction.
  12. Name the compound used for testing CO2 gas.

Some Other Question for class 10 Science Chapter 1

Q1.  What happens chemically when quick lime is added to water?

Q2.  How will you test for the gas which is liberated when HCL reacts with an active metal?

Q3.  What is an oxidation reaction? Is it exothermic or endothermic? Give one example of oxidation Reaction.

Q4.  Give an example of photochemical reaction.

Q5.  Give an example of a decomposition reaction. Describe any activity to illustrate such a reaction by heating.

Q6.  Why is respiration considered as exothermic process?

Q7.  Balance the following chemical equation.

           Fe(s) +H2O(g) = Fe3O4 + H2(g)

           MnO2 + HCL = MnCl2 + Cl2 + H2O

           HNO3 + Ca(OH)2 = Ca(NO3)2 + H2O

Q8.  On what basis is a chemical equation balanced?

Q9.  State any two observations in an activity suggesting the occurrence of a chemical reaction.

Q10.  Name a reducing agent which may be used to obtain manganese from manganese dioxide.

Q11.  What change in colour is observed when silver chloride is left exposed to sunlight? Also mention the type of chemical reaction.

Q12.  Define a combination reaction. Give one example of an exothermic combination reaction.

Q13.  What is observed when a solution of potassium iodide is added to lead nitrate solution?

              What type of reaction is this? Write a balanced chemical equation for this reaction.

Q14.  Distinguish between an exothermic and an endothermic reaction.

Q15.  Distinguish between a displacement and a double displacement reaction.

Q16.  Identify the type of reaction in the following:

              Fe + CuSO4(aq) = FeSO4(aq) + Cu(s)

              2H2 + O2 = 2H2O

Previous Year Board Exam Paper Questions for Class 10 Science chapter 1

1.  How will you test for a gas which is liberated when HCL reacts with an active metal?      (CBSE 2008)

2.  What is baking powder? How does it make the cake soft and spongy?      (CBSE 2008)

3.  When fresh milk is changed into curd will its pH value increase or decrease? Why?

4.  Give Arrhenius definition of an acid and a base.      (CBSE 2009)

5.  What happens chemically when quick lime is added to water?      (CBSE 2008)

6.  Name the gas evolved when dilute HCL reacts with Sodium hydrogen carbonate. How is it recognized?      (CBSE 2008)

7.  How does the flow of acid rain water into a river make the survival of aquatic life in the river difficult?      (CBSE 2008)

8.  How is the pH of a solution of an acid influenced when it is diluted?      (CBSE 2008 F)

9.  How does the pH of the solution change when a solution of base is diluted?      (CBSE 2008 F)

10.  Arrange these in increasing order of their pH values- NaOH, blood, lemon juice.      (CBSE 2008 F)

11.  Two solutions of A and B have pH values of 5 and 8. Which solution will be basic in nature?      (CBSE 2008 C)

12.  Why does tooth decay start when pH of mouth is lower than 5.5?      (CBSE 2009)

13.  What would be the colour of litmus in a solution of sodium carbonate?      (CBSE 2009)

14.  Name the products obtained when sodium hydrogen carbonate is heated. Write the chemical equation for the same.      (AI CBSE 2009)

15.  Write the chemical formula of washing soda and baking soda. Which one of these two is an ingredient of antacids? How does it provide relief in stomachache?      (CBSE 2008 F)

16.  What do you mean by water of crystallization of a substance? Describe an activity to show that blue copper sulphate crystals contain water of crystallization.      (CBSE 2009 F)

17.  How can washing soda be obtained from baking soda? Name an industrial use of washing soda other than washing clothes.      (AI CBSE 2008)

18.  Why does 1 M HCL solutions have a higher concentration of H+ ions than 1M CH3COOH solution?      (AI CBSE 2009)

Other Important Questions Answer and Solution Notes for Class 10 Science Chapter 1

What is Chemical Reactions? Explain with Example.

The transformation of chemical substance into another chemical substance is known as Chemical Reaction.
Example:   Rusting of iron, Formation curd, Digestion of food, Respiration, etc.

NCERT Solution for class 10 Science Chapter 1 Chemical reactions and equations

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

(a) Thermal decomposition reaction (Thermolysis)
Decomposition of potassium chlorate (KClO3) : When heated strongly, potassium chlorate decomposes into potassium chloride and oxygen. This reaction is used for the preparation of oxygen.
2KClO3 + Heat → 2KCl + 3O2

(b) Electrolytic decomposition reaction (Electrolysis)
Decomposition of sodium chloride (NaCl) : On passing electricity through molten sodium chloride, it decomposes into sodium and chlorine.
NaCl → Na + Cl2

(c) Photo decomposition reaction (Photolysis)
Decomposition of hydrogen peroxide (H2O2): In the presence of light, hydrogen peroxide decomposes into water and oxygen.

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

A displacement reaction is the one when a more reactive substance displaces a less reactive one from its salt solution whereas a double displacement reaction is the one where a mutual exchange of ions happens between two compounds.
In a displacement reaction, only a single displacement takes place whereas in the double displacement reaction, as the name suggests two displacement takes place between the molecules.
Displacement reaction
Mg + 2HCl → MgCl2 + H2
Double displacement reaction
2KBr + BaI2 → 2KI + BaBr2

2H2O2 (Light)→ 2H2O + O2

Class 10 Science Chapter 1 Test Book Question Answer

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

    Magnesium rubber should be cleaned before burning in air because Magnesium metal reacts with the atmospheric oxygen and forms Magnesium Oxide (MgO) layer which is a very stable compound. In order to prevent further reactions with Oxygen, it is therefore necessary to clean the ribbon by to remove
    the layer of MgO.
  1. Write a balanced equations 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 → 2AlCl3 + 3BaSO4
    iii) 2Na + 2H2O → 2NaOH + H2
  1. Write a balanced chemical equation with state symbols for the following reactions
    i) Solutions of Barium chloride and Sodium sulphate in water react to give insoluble Barium sulphate and solution of Sodium chloride.
    ii) Sodium hydroxide solution in water reacts with hydrochloric acid solution to produce Sodium chloride solution and water.

    Solution:
    i) BaCl2 + Na2SO4 → BaSO4 + 2NaCl
    ii) NaOH + HCl → NaCl + H2O
  2. 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 in (i) above with water.
    Solution:
    i)The substance ‘X’ which is used in whitewashing is quick lime or Calcium Oxide and its formula is CaO.
    ii)
    CaO + H2O → Ca(OH)2
  3. 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

Solution: In activity 1.7, gas collected in one of the test tubes is double of the amount collected in the other because water gets hydrolysed to release H2 and O2 gas. Here, after electrolysis two molecules of Hydrogen and one molecule of oxygen gas is released, hence the amount of Hydrogen collected would be double than that of oxygen.

Youtube Class 10 Science Chapter 1 Video

Class 10 Science Chapter 1 FAQ Chemical Reactions and Equations

What is Chemical Reactions ?

A chemical reaction is a process in which the initial substances change to form a new substance. Chemical reactions involve chemical changes.

Other Solution

The reaction through which the chemical properties of a substance are changed is called a chemical reaction.

What is Chemical Equation ?

Chemical Equation are representation of chemical reaction by means of symbols of substances in the form of formula is called chemical equation.

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

Magnesium gets covered with a layer of magnesium oxide when kept in air for a long time. This layer hinders the burning of magnesium. Hence, it is to be cleaned before burning.

Other Solution

Magnesium rubber should be cleaned before burning in air because Magnesium metal reacts with the atmospheric oxygen and forms Magnesium Oxide (MgO) layer which is a very stable compound. In order to prevent further reactions with Oxygen, it is therefore necessary to clean the ribbon by to remove the layer of MgO.

Types of Chemical Reaction?(Change in State)

(i) Physical Change
(ii) Chemical Change

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

A balanced equation is the one in which number of different atoms on both the reactant and product sides are equal. Balancing chemical equation is necessary for the reaction should obey The Law of Conservation of energy. Balancing the chemical equation has no defined method and is purely a trial and error attempt.

What are Balanced Chemical Equation ?

A balanced chemical equation has an equal number of atoms of different elements in the reactants and products.
The chemical equations should be balanced to satisfy the law of conservation of mass.

How much types of Chemical Reaction ?

these are basically five types:
i. Combination Reaction
ii. Decomposition Reaction
iii. Displacement Reaction
iv. Double Displacement Reaction
v. Redox Reaction

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

An endothermic reaction occurs when energy is absorbed from the surroundings in the form of heat.(Example: Photosynthesis, melting of ice, evaporation). Conversely, an exothermic reaction is one in which energy is released from the system into the surroundings. (Example: Explosions, concrete setting, nuclear fission and fusion).

Why is respiration considered to be an exothermic reaction?

For the survival of life, we require energy. We obtain this energy from the food we eat. The food molecules, through the process of digestion, is broken down into a simpler molecule like glucose. These substances come in contact with the Oxygen present in our body cells to form Carbon dioxide and water along with a certain amount of energy (Respiration process). Since the energy is in the form of heat (that maintains our body temperature) the respiration is considered to be an exothermic reaction.
The reaction taking place is:

C6H12O6 + 6O2 → 6CO2 + 6H2O + Energy

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

Combination reaction is said to be the reaction between two or more molecules to form a larger molecule; whereas the decomposition reaction is defined as the splitting of larger molecules into two or more smaller molecules. This essentially explains that the decomposition reaction is the opposite of the combination reaction.
In most of the cases the decomposition reaction is endothermic since heat from the surrounding or induced heat is used to break the bonds of the larger molecule. Few examples of decomposition reactions are:
ZnCO3 → ZnO + CO2
CaCO3 + Energy → CaO + CO2
2HgO → 2Hg + O2

What is Corrosion?

It is an undesirable change that occurs in metals when they are attacked by moisture, air, acids, and bases.
Example: Corrosion (rusting) of Iron: Fe2O3.nH2O (Hydrated iron oxide)

What is Rancidity?

The taste and odor of food materials containing fat and oil change when they are left exposed to air for a long time. This is called Rancidity. It is caused due to the oxidation of fat and oil present in food materials.

Methods to prevent rancidity?

By adding anti-oxidant.
Vacuum packing.
Replacing air by nitrogen.
Refrigeration of foodstuff.