NCERT Solutions for Class 10 Science Chapter 1: Chemical Reactions and Equations
Are you looking for the best and accurate NCERT Solutions for Class 10 Science Chapter 1? If yes, then you have come to the right place. In this article, we will provide you with the free PDF download of the NCERT Solutions for Class 10 Science Chapter 1 Chemical Reactions and Equations. These solutions are prepared by our expert teachers as per the latest CBSE syllabus and NCERT guidelines. You can use these solutions to revise the chapter and practice the questions for the board exam.
Introduction
Chapter 1 of Class 10 Science deals with the basic concepts of chemical reactions and equations. You will learn about the following topics in this chapter:
ncert solutions for class 10 science chapter 1 pdf download
What are chemical reactions and equations?
How to write and balance chemical equations?
What are the types of chemical reactions?
What are the effects of chemical reactions in our daily life?
Let us start with the first topic.
What are chemical reactions and equations?
A chemical reaction is a process in which one or more substances (reactants) undergo a change to form one or more new substances (products) with different properties. For example, when magnesium ribbon burns in air, it forms magnesium oxide, a new substance.
A chemical equation is a symbolic representation of a chemical reaction. It shows the reactants and products along with their physical states, proportions, and conditions. For example, the chemical equation for the burning of magnesium ribbon is:
Magnesium + Oxygen Magnesium oxide
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Mg (s) + O2 (g) MgO (s)
The substances on the left side of the arrow are called reactants and the substances on the right side of the arrow are called products. The symbols (s), (g), and (l) indicate the physical states of the substances: solid, gas, and liquid respectively.
How to write and balance chemical equations?
To write a chemical equation, we need to know the names and formulas of the reactants and products involved in the reaction. We also need to follow some rules to write a correct and complete chemical equation. These rules are:
The reactants are written on the left side of the arrow and the products are written on the right side of the arrow.
The physical states of the reactants and products are mentioned in brackets after their names or formulas.
The plus sign (+) is used to separate two or more reactants or products.
The arrow sign () is used to indicate the direction of the reaction.
The coefficients (numbers) are used to indicate the number of moles or molecules of each substance involved in the reaction.
The symbols such as Δ (heat), (light), (electricity), etc. are used to indicate the conditions required for the reaction.
To balance a chemical equation, we need to ensure that the number of atoms of each element is equal on both sides of the arrow. This is based on the law of conservation of mass, which states that matter can neither be created nor destroyed in a chemical reaction. To balance a chemical equation, we can follow these steps:
Write down the unbalanced equation using correct formulas and physical states of reactants and products.
Count the number of atoms of each element on both sides of the arrow.
Start with an element that appears only once on each side. Adjust the coefficients of that element by using suitable numbers. Do not change the subscripts of the formulas.
Repeat the same process for other elements that appear only once on each side.
Move on to the elements that appear more than once on each side. Adjust the coefficients of those elements by using suitable numbers. Do not change the subscripts of the formulas.
Check if the equation is balanced by counting the number of atoms of each element on both sides of the arrow. If not, repeat the steps until the equation is balanced.
For example, let us balance the following equation:
Fe (s) + H2O (g) Fe3O4 (s) + H2 (g)
The unbalanced equation has 1 atom of Fe, 2 atoms of H, and 1 atom of O on the left side, and 3 atoms of Fe, 2 atoms of H, and 4 atoms of O on the right side.
We start with Fe, which appears only once on each side. To make the number of Fe atoms equal on both sides, we put a coefficient of 3 before Fe on the left side.
3Fe (s) + H2O (g) Fe3O4 (s) + H2 (g)
Now we have 3 atoms of Fe, 2 atoms of H, and 1 atom of O on the left side, and 3 atoms of Fe, 2 atoms of H, and 4 atoms of O on the right side.
We move on to H, which appears more than once on each side. To make the number of H atoms equal on both sides, we put a coefficient of 4 before H2O on the left side and a coefficient of 2 before H2 on the right side.
3Fe (s) + 4H2O (g) Fe3O4 (s) + 2H2 (g)
Now we have 3 atoms of Fe, 8 atoms of H, and 4 atoms of O on the left side, and 3 atoms of Fe, 8 atoms of H, and 4 atoms of O on the right side.
The equation is balanced as the number of atoms of each element is equal on both sides. We can write it in a simplified form by removing the common factors from the coefficients.
The balanced equation is:
Fe (s) + 2H2O (g) Fe2O3 (s) + H2 (g)
What are the types of chemical reactions?
A chemical reaction can be classified into different types based on the nature and characteristics of the reactants and products. Some common types of chemical reactions are:
Synthesis or combination reaction: A reaction in which two or more substances combine to form a single product. For example,
Metal + Non-metal Salt
Zn (s) + S (s) ZnS (s)
Metal oxide + Water Metal hydroxide
CuO (s) + H2O (l) Cu(OH)2(aq)
Metal + Oxygen Metal oxide
Mg (s) + O2(g) MgO (s)
Degradation or decomposition reaction:A reaction in which a single compound breaks down into two or more simpler substances. For example,
Salt Metal + Non-metal
CuCl2(aq) Cu(s) + Cl2(g)
Metal carbonate Metal oxide + Carbon dioxide
CaCO3(s) CaO(s) + CO2(g ))
Metal hydroxide Metal oxide + Water
Ca(OH)2(s) CaO(s) + H2O (l)
Displacement or substitution reaction:A reaction in which a more reactive element displaces a less reactive element from its compound. For example,
Metal + Salt solution Metal salt + Metal
Zn (s) + CuSO4(aq) ZnSO4(aq) + Cu (s)
Metal + Acid Salt + Hydrogen
Mg (s) + 2HCl (aq) MgCl2(aq) + H2(g)
Non-metal + Salt solution Non-metal salt + Non-metal
Cl2(g) + 2NaBr (aq) 2NaCl (aq) + Br2(l)
Double displacement or exchange reaction:A reaction in which two compounds exchange their ions to form two new compounds. For example,
Salt solution + Salt solution Salt solution + Salt solution
AgNO3(aq) + NaCl (aq) AgCl (s) + NaNO3(aq)
Acid + Base Salt + Water
HCl (aq) + NaOH (aq) NaCl (aq) + H2O (l)
Oxidation and reduction reaction:A reaction in which one or more elements undergo a change in their oxidation states. Oxidation is the loss of electrons or increase in oxidation state, and reduction is the gain of electrons or decrease in oxidation state. For example,
Zn (s) + CuSO4(aq) ZnSO4(aq) + Cu (s)
In this reaction, Zn loses two electrons and increases its oxidation state from 0 to +2. This is oxidation.
Cu gains two electrons and decreases its oxidation state from +2 to 0. This is reduction.
The substance that causes oxidation is called the oxidizing agent, and the substance that causes reduction is called the reducing agent. In this case, CuSO4 is the oxidizing agent and Zn is the reducing agent.
NCERT Solutions for Class 10 Science Chapter 1
In this section, we will provide you with the NCERT Solutions for Class 10 Science Chapter 1 Chemical Reactions and Equations. These solutions are based on the NCERT textbook and are explained in a simple and easy manner. You can use these solutions to understand the concepts and solve the questions given in the chapter.
The chapter has two sets of in-text questions and one set of exercise questions at the end of the chapter. We will provide you with the solutions for all these questions.
In-text questions set 1
This set of questions is given on page 6 of the NCERT textbook. The questions are based on the topic of writing and balancing chemical equations.
Question 1
Why should a magnesium ribbon be cleaned before burning in air?
Solution:
A magnesium ribbon should be cleaned before burning in air because it has a thin layer of magnesium oxide on its surface. This layer prevents the magnesium from reacting with oxygen in air. By cleaning the ribbon with sandpaper, we remove this layer and expose the fresh metal to air.
Question 2
Write the balanced equation for the following chemical reactions:
(i) Hydrogen + Chlorine Hydrogen chloride
(ii) Barium chloride + Aluminium sulphate Barium sulphate + Aluminium chloride (iii) Sodium + Water Sodium hydroxide + Hydrogen
Solution:
The balanced equations for the given chemical reactions are:
(i) Hydrogen + Chlorine Hydrogen chloride
H2 (g) + Cl2 (g) 2HCl (g)
(ii) Barium chloride + Aluminium sulphate Barium sulphate + Aluminium chloride
3BaCl2 (aq) + Al2(SO4)3 (aq) 3BaSO4 (s) + 2AlCl3 (aq)
(iii) Sodium + Water Sodium hydroxide + Hydrogen
2Na (s) + 2H2O (l) 2NaOH (aq) + H2 (g)
Question 3
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 the solution of sodium chloride.
(ii) Sodium hydroxide solution (in water) reacts with hydrochloric acid solution (in water) to produce sodium chloride solution and water.
Solution:
The balanced chemical equations with state symbols for the given reactions are:
(i) Solutions of barium chloride and sodium sulphate in water react to give insoluble barium sulphate and the solution of sodium chloride.
BaCl2 (aq) + Na2SO4 (aq) BaSO4 (s) + 2NaCl (aq)
(ii) Sodium hydroxide solution (in water) reacts with hydrochloric acid solution (in water) to produce sodium chloride solution and water.
NaOH (aq) + HCl (aq) NaCl (aq) + H2O (l)
In-text questions set 2
This set of questions is given on page 10 of the NCERT textbook. The questions are based on the topic of types of chemical reactions.
Question 1
A solution of a substance X is used for white washing.
(i) Name the substance X and write its formula.
(ii) Write the reaction of the substance X named in (i) above with water.
Solution:
The substance X is calcium oxide and its formula is CaO.
(i) The substance X is calcium oxide and its formula is CaO.
(ii) The reaction of calcium oxide with water is:
CaO (s) + H2O (l) Ca(OH)2(aq)
This reaction is a synthesis or combination reaction.
Question 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.
Solution:
The amount of gas collected in one of the test tubes in Activity 1.7 is double of the amount collected in the other because the ratio of hydrogen and oxygen produced by the electrolysis of water is 2:1. The gas that is collected in double amount is hydrogen.
Question 3
Write the balanced chemical equation for the following and identify the type of reaction in each case.
(i) Potassium bromide(aq) + Barium iodide(aq) Potassium iodide(aq) + Barium bromide(s)
(ii) Zinc carbonate(s) Zinc oxide(s) + Carbon dioxide(g)
(iii) Hydrogen(g) + Chlorine(g) Hydrogen chloride(g)
(iv) Magnesium(s) + Hydrochloric acid(aq) Magnesium chloride(aq) + Hydrogen(g)
Solution:
The balanced chemical equations and the types of reactions for the given cases are:
(i) Potassium bromide(aq) + Barium iodide(aq) Potassium iodide(aq) + Barium bromide(s)
2KBr (aq) + BaI2 (aq) 2KI (aq) + BaBr2 (s)
This reaction is a double displacement or exchange reaction.
(ii) Zinc carbonate(s) Zinc oxide(s) + Carbon dioxide(g)
ZnCO3 (s) ZnO (s) + CO2 (g)
This reaction is a degradation or decomposition reaction.
(iii) Hydrogen(g) + Chlorine(g) Hydrogen chloride(g)
H2 (g) + Cl2 (g) 2HCl (g)
This reaction is a synthesis or combination reaction.
(iv) Magnesium(s) + Hydrochloric acid(aq) Magnesium chloride(aq) + Hydrogen(g)
Mg (s) + 2HCl (aq) MgCl2 (aq) + H2 (g)
This reaction is a displacement or substitution reaction.
Exercise questions
This set of questions is given at the end of the chapter on page 13 of the NCERT textbook. The questions are based on the various topics covered in the chapter.
Question 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 oxidised.
(c) Carbon is getting oxidised.
(d) Lead oxide is getting reduced.
Solution:
The statements that are incorrect are:
(b) Carbon dioxide is getting oxidised.
(d) Lead oxide is getting reduced.
In this reaction, lead oxide is getting oxidised as it loses oxygen and its oxidation state decreases from +2 to 0. Carbon is getting reduced as it gains oxygen and its oxidation state increases from 0 to +4. Carbon dioxide is neither getting oxidised nor reduced as its oxidation state remains the same at +4.
Question 2
The following is an incomplete equation for a chemical reaction:
X(s)+Y(aq)->Z(aq)+W(g)
All four substances are in their standard states. Identify X, Y, Z, and W by matching them with the substances from the list given below:
Potassium bromide, zinc, hydrogen, zinc bromide, potassium, hydrogen bromide.
Solution:
The correct equation for the chemical reaction is:
Zn(s)+2HBr(aq)->ZnBr2(aq)+H2(g)
X is zinc, Y is hydrogen bromide, Z is zinc bromide, and W is hydrogen.
Question 3
Balanced 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:
The balanced chemical equations are:
(a)HNO3+Ca(OH)2->Ca(NO3)2+H2O
2HNO3(aq)+Ca(OH)2(aq)->Ca(NO3)2(aq)+2H2O(l)
This reaction is a double displacement or exchange reaction.
(b)NaOH+H2SO4->Na2SO4+H2O
2NaOH(aq)+H2SO4(aq)->Na2SO4(aq)+2H2O(l)
This reaction is a double displacement or exchange reaction.
(c)NaCl+AgNO3->AgCl+NaNO3
NaCl(aq)+AgNO3(aq)->AgCl(s)+NaNO3(aq)
This reaction is a double displacement or exchange reaction.
(d)BaCl2+H2SO4->BaSO4+HCl
BaCl2(aq)+H2SO4(aq)->BaSO4(s)+2HCl(aq)
This reaction is a double displacement or exchange reaction.
To be continued...
I hope you enjoyed reading this article and found it helpful. If you have any questions or feedback, please feel free to leave a comment below. Thank you for your time and attention.
Frequently Asked Questions (FAQs)
In this section, we will answer some of the common questions that students may have about the NCERT Solutions for Class 10 Science Chapter 1 Chemical Reactions and Equations.
#1. Why do we need to balance chemical equations?
We need to balance chemical equations to follow the law of conservation of mass, which states that matter can neither be created nor destroyed in a chemical reaction. Balancing chemical equations ensures that the number of atoms of each element is equal on both sides of the arrow, and that the mass of the reactants is equal to the mass of the products.
#2. What are the indicators of a chemical reaction?
The indicators of a chemical reaction are:
A change in colour, odour, or state of the substances involved.
A formation of a precipitate, a gas, or a new substance with different properties.
A release or absorption of heat, light, sound, or electricity.
A change in the temperature or pH of the system.
A change in the rate of reaction or equilibrium position.
A change in the oxidation states or valencies of the elements involved.
#3. What 44f88ac181