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

NCERT Solutions for Class 10 Science Chapter 1 Chemical Reactions and Equations includes all important topics with detailed explanations to help students understand concepts better and score higher marks in board examinations.

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Intex Questions - Page Number: 1

Q1: Why should a magnesium ribbon be cleaned before burning in air?
Answer: Magnesium gets covered with a protective layer of magnesium oxide when stored in air for a long time. This oxide layer hinders the burning of magnesium. Hence, it needs to be cleaned using sandpaper before burning.
Q2: Write the balanced equation for the following chemical reactions:

(i) Hydrogen + Chlorine → Hydrogen chloride
Equation: H2 + Cl2 → 2HCl

(ii) Barium chloride + Aluminium sulphate → Barium sulphate + Aluminium chloride
Equation: 3BaCl2 + Al2(SO4)3 → 3BaSO4 + 2AlCl3

(iii) Sodium + Water → Sodium hydroxide + Hydrogen
Equation: 2Na + 2H2O → 2NaOH + H2↑

Q3: 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.
Equation: 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.
Equation: NaOH (aq) + HCl (aq) → NaCl (aq) + H2O (l)

Intext Questions - Page Number: 10

Q1: A solution of a substance 'X' is used for whitewashing.

(i) Name the substance 'X' and write its formula.
Answer: Quick lime (Calcium Oxide), Formula: CaO.

(ii) Write the reaction of the substance 'X' named in (i) above with water.
Equation: CaO (s) + H2O (l) → Ca(OH)2 (aq) + Heat

Q2: 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.
Answer: During the electrolysis of water, water breaks down into Hydrogen and Oxygen in a 2:1 ratio by volume:
2H2O (l) → 2H2 (g) + O2 (g)
Therefore, the volume of Hydrogen gas collected at the cathode is double the volume of Oxygen gas collected at the anode.

Intext Questions - Page Number: 13

Q1: Why does the colour of copper sulphate solution change when an iron nail is dipped in it?
Answer: When an iron nail is dipped in blue copper sulphate solution, iron displaces copper because it is more reactive. Iron sulphate is formed, turning the blue solution into light green:
Fe (s) + CuSO4 (aq) → FeSO4 (aq) + Cu (s)
Q2: Give an example of a double displacement reaction other than the one given in Activity 1.10.
Answer: Reaction between Sodium hydroxide and Hydrochloric acid:
NaOH (aq) + HCl (aq) → NaCl (aq) + H2O (l)
Q3: Identify the substances that are oxidised and reduced in the following reactions:

(i) 4Na(s) + O2(g) → 2Na2O(s)
Substance Oxidised: Na (Gains Oxygen)
Substance Reduced: O2

(ii) CuO(s) + H2(g) → Cu(s) + H2O(l)
Substance Oxidised: H2 (Gains Oxygen)
Substance Reduced: CuO (Loses Oxygen)

Textbook Chapter End Exercise Questions

Q1: 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.

Correct Answer: (i) (a) and (b)

Q2: Fe2O3 + 2Al → Al2O3 + 2Fe. The above reaction is an example of a:
Answer: (d) Displacement reaction.
Q3: What happens when dilute hydrochloric acid is added to iron filings?
Answer: (a) Hydrogen gas and iron chloride are produced.
Q4: What is a balanced chemical equation? Why should chemical equations be balanced?
Answer: A balanced chemical equation has an equal number of atoms of each element on both the reactant and product sides. Equations must be balanced to satisfy the Law of Conservation of Mass, which states that mass can neither be created nor destroyed in a chemical reaction.
Q9: What does one mean by exothermic and endothermic reactions? Give examples.

Exothermic Reactions: Reactions in which heat is released along with products.
Example: C (s) + O2 (g) → CO2 (g) + Heat

Endothermic Reactions: Reactions in which heat energy is absorbed.
Example: N2 (g) + O2 (g) + Heat → 2NO (g)

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