CBSE Class 10 Science Chemical Reactions and Equations MCQs Set 11

Download CBSE MCQs for Class 10 Science: Chapter 01 Chemical Reactions and Equations

Access targeted multiple-choice questions for Chapter 01 Chemical Reactions and Equations designed to align with the latest CBSE academic syllabus for Class 10 Science. These objective practice sets help students evaluate their conceptual understanding and improve exam readiness.

Chapter-wise Objective Questions: Chapter 01 Chemical Reactions and Equations

Navigate directly to the 50 objective questions for Chapter 01 Chemical Reactions and Equations using the digital viewer below. Each practice set includes verified answer keys, allowing students to instantly cross-check their work and identify areas requiring further revision.

Here are 35 Class 10 Science MCQs with explained answers from Chemical Reactions and Equations. They test redox reactions, oxidising and reducing agents, exothermic and endothermic changes, and the products and observations of common laboratory activities.

Multiple Choice Questions

Question 1: A substance which oxidises itself and reduces other is known as
(a) oxidising agent
(b) reducing agent
(c) both of these
(d) none of these
Show Answer & Explanation

Answer: (b) reducing agent

Explanation:
1. A reducing agent removes oxygen from another substance and is itself oxidised.
2. So the answer is a reducing agent.

Teacher's Note:
1. The agent is the opposite of what happens to it.
2. An oxidising agent is itself reduced.

Question 2: A redox reaction is one in which
(a) both the substances are reduced
(b) both the substances are oxidised
(c) an acid is neutralised by the base
(d) one substance is oxidised while the other is reduced
Show Answer & Explanation

Answer: (d) one substance is oxidised while the other is reduced

Explanation:
1. Oxidation and reduction always occur together.
2. One reactant gains oxygen (is oxidised) while the other loses oxygen (is reduced).

Teacher's Note:
1. Redox joins reduction and oxidation.
2. They cannot occur separately.

Question 3: CuO + H2 → H2O + Cu. The reaction is an example of
(a) redox reaction
(b) synthesis reaction
(c) neutralisation
(d) analysis reaction
Show Answer & Explanation

Answer: (a) redox reaction

Explanation:
1. CuO loses oxygen (reduced) and H2 gains oxygen (oxidised).
2. Both happen together, so it is a redox reaction.

Teacher's Note:
1. Find who gains and who loses oxygen.
2. Both processes in one reaction means redox.

Question 4: Which of the following is termed as an oxidising agent?
(a) Which gives oxygen
(b) Which removes oxygen
(c) Which gives hydrogen
(d) All of the above
Show Answer & Explanation

Answer: (a) Which gives oxygen

Explanation:
1. An oxidising agent gives oxygen to (or removes hydrogen from) another substance.
2. Removing oxygen or giving hydrogen are properties of reducing agents.

Teacher's Note:
1. The oxidising agent is reduced.
2. Oxygen is a common oxidising agent.

Question 5: Which of the following is termed as a reducing agent?
(a) Which gives oxygen
(b) Which removes oxygen
(c) Which removes hydrogen
(d) All of the above
Show Answer & Explanation

Answer: (b) Which removes oxygen

Explanation:
1. A reducing agent removes oxygen from (or gives hydrogen to) another substance.
2. Giving oxygen or removing hydrogen are properties of oxidising agents.

Teacher's Note:
1. A reducing agent is itself oxidised.
2. Hydrogen and carbon are common reducing agents.

Question 6: Which of the following shows an oxidation reaction?
(a) Gain of oxygen
(b) Loss of oxygen
(c) Gain of hydrogen
(d) None of the above
Show Answer & Explanation

Answer: (a) Gain of oxygen

Explanation:
1. Oxidation is the addition of oxygen or removal of hydrogen.
2. So gain of oxygen is oxidation.

Teacher's Note:
1. Oxidation: gain of O or loss of H.
2. Reduction: loss of O or gain of H.

Question 7: Which of the following shows a reduction reaction?
(a) Gain of oxygen
(b) Loss of oxygen
(c) Loss of hydrogen
(d) None of the above
Show Answer & Explanation

Answer: (b) Loss of oxygen

Explanation:
1. Reduction is the removal of oxygen or addition of hydrogen.
2. So loss of oxygen is reduction.

Teacher's Note:
1. Reduction is the opposite of oxidation.
2. Loss of oxygen reduces a substance.

Question 8: MnO2 + 4HCl → MnCl2 + 2H2O + Cl2. The reaction given above is a redox reaction because in this case
(a) MnO2 is oxidised and HCl is reduced
(b) HCl is oxidised
(c) MnO2 is reduced
(d) MnO2 is reduced and HCl is oxidised
Show Answer & Explanation

Answer: (d) MnO2 is reduced and HCl is oxidised

Explanation:
1. MnO2 loses oxygen, so it is reduced.
2. HCl loses hydrogen to form Cl2, so it is oxidised. Both happen, so (d) is the complete statement.

Teacher's Note:
1. Oxygen loss means reduction and hydrogen loss means oxidation.
2. Both occur together.

Question 9: 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
(a) (a) and (b)
(b) (a) and (c)
(c) (a), (b) and (c)
(d) all
Show Answer & Explanation

Answer: (a) (a) and (b)

Explanation:
1. PbO loses oxygen to give Pb, so lead oxide is reduced; carbon gains oxygen to give CO2, so carbon is oxidised.
2. Statement (a) is wrong because lead metal is a product, and (b) is wrong because CO2 is a product. So (a) and (b) are incorrect.

Teacher's Note:
1. Reactants are oxidised or reduced, not the products.
2. Be careful with the word incorrect.

Question 10: Which of the following statements about the given reaction are correct? 3Fe(s) + 4H2O(g) → Fe3O4(s) + 4H2(g)
(i) Iron metal is getting oxidised (ii) Water is getting reduced (iii) Water is acting as a reducing agent (iv) Water is acting as an oxidising agent
(a) (i), (ii) and (iii)
(b) (iii) and (iv)
(c) (i), (ii) and (iv)
(d) (ii) and (iv)
Show Answer & Explanation

Answer: (c) (i), (ii) and (iv)

Explanation:
1. Iron gains oxygen, so it is oxidised; water loses oxygen, so it is reduced.
2. The substance reduced acts as the oxidising agent, so water is an oxidising agent.

Teacher's Note:
1. The reduced substance is the oxidising agent.
2. Iron is the reducing agent.

Question 11: Select the oxidising agent for the following reaction: H2S + I2 → 2HI + S
(a) I2
(b) H2S
(c) HI
(d) S
Show Answer & Explanation

Answer: (a) I2

Explanation:
1. H2S loses hydrogen, so it is oxidised and is the reducing agent.
2. I2 gains hydrogen, so it is reduced and acts as the oxidising agent.

Teacher's Note:
1. The substance that is reduced is the oxidising agent.
2. Hydrogen gain is reduction.

Question 12: The reaction between iron oxide and hydrogen is Fe3O4 + 4H2 → 3Fe + 4H2O. Which option shows the compounds undergoing oxidation and reduction?
(a) Oxidation: 4H2; reduction: Fe3O4
(b) Oxidation: Fe3O4; reduction: 4H2O
(c) Oxidation: 4H2O; reduction: Fe3O4
(d) Oxidation: 3Fe; reduction: 4H2
Show Answer & Explanation

Answer: (a) Oxidation: 4H2; reduction: Fe3O4

Explanation:
1. Hydrogen gains oxygen to form water, so it is oxidised.
2. Fe3O4 loses oxygen to form iron, so it is reduced.

Teacher's Note:
1. Check who gains and who loses oxygen.
2. Hydrogen is the reducing agent.

Question 13: In the reaction Fe3O4(s) + 4H2(g) → 3Fe(s) + 4H2O(g), identify the oxidising agent, reducing agent and the substance oxidised.
(a) Oxidising agent: H2O; reducing agent: Fe; substance oxidised: H2
(b) Oxidising agent: Fe3O4; reducing agent: H2; substance oxidised: H2O
(c) Oxidising agent: H2; reducing agent: Fe3O4; substance oxidised: Fe3O4
(d) Oxidising agent: Fe3O4; reducing agent: H2; substance oxidised: H2
Show Answer & Explanation

Answer: (d) Oxidising agent: Fe3O4; reducing agent: H2; substance oxidised: H2

Explanation:
1. Fe3O4 loses oxygen, so it is reduced and acts as the oxidising agent.
2. H2 gains oxygen, so it is oxidised and is the reducing agent.

Teacher's Note:
1. The oxidised substance and the reducing agent are the same.
2. The reduced substance and the oxidising agent are the same.

Question 14: When the powder of a common metal is heated in an open china dish, its colour turns black. However, when hydrogen is passed over the hot black substance so formed, it regains its original colour. What type of chemical reaction takes place in each of the two given steps?
(a) First oxidation reaction, then displacement reaction
(b) First combustion reaction, then reduction reaction
(c) First oxidation reaction, then redox reaction
(d) First reduction reaction, then redox reaction
Show Answer & Explanation

Answer: (c) First oxidation reaction, then redox reaction

Explanation:
1. Copper powder gains oxygen on heating to form black CuO: oxidation.
2. CuO + H2 → Cu + H2O: CuO is reduced and H2 is oxidised, a redox reaction.

Teacher's Note:
1. Copper is the metal whose colour changes in both steps.
2. The second step is a redox reaction.

Question 15: A reddish-brown residue is obtained when dry hydrogen is passed over a heated oxide of metal M. This residue could be
(a) lead
(b) silver
(c) copper
(d) zinc
Show Answer & Explanation

Answer: (c) copper

Explanation:
1. Hydrogen reduces copper(II) oxide to copper metal.
2. Copper is reddish brown; lead and zinc are grey and silver is white.

Teacher's Note:
1. Reddish brown is the colour of copper metal.
2. Hydrogen does not reduce zinc oxide.

Question 16: When copper powder is heated, it gets coated with
(a) black copper oxide
(b) yellow copper oxide
(c) red copper oxide
(d) none of these
Show Answer & Explanation

Answer: (a) black copper oxide

Explanation:
1. 2Cu + O2 → 2CuO
2. Copper(II) oxide is black.

Teacher's Note:
1. Copper changes from reddish brown to black.
2. Hydrogen restores the brown colour.

Question 17: Combination of phosphorus and oxygen is an example of
(a) oxidation
(b) reduction
(c) rancidity
(d) none of these
Show Answer & Explanation

Answer: (a) oxidation

Explanation:
1. Phosphorus gains oxygen to form its oxide.
2. Gain of oxygen is oxidation.

Teacher's Note:
1. Burning of an element in oxygen is oxidation.
2. Reduction is loss of oxygen.

Question 18: Formation of CuO from copper and oxygen denotes
(a) reduction
(b) oxidation
(c) redox reaction
(d) none of these
Show Answer & Explanation

Answer: (b) oxidation

Explanation:
1. Copper gains oxygen to form CuO.
2. Gain of oxygen is oxidation.

Teacher's Note:
1. Copper gains oxygen, so the change is oxidation.
2. Redox describes the whole reaction, not this single change.

Question 19: What is the colour of the ash formed when a magnesium ribbon is burnt in air?
(a) White
(b) Black
(c) Yellow
(d) Pink
Show Answer & Explanation

Answer: (a) White

Explanation:
1. 2Mg + O2 → 2MgO
2. Magnesium burns with a dazzling white flame and forms white magnesium oxide.

Teacher's Note:
1. Never look directly at burning magnesium.
2. MgO is a white powder.

Question 20: Why is a magnesium ribbon cleaned before burning?
(a) To remove dust
(b) To remove magnesium oxide
(c) To remove magnesium
(d) All of the above
Show Answer & Explanation

Answer: (b) To remove magnesium oxide

Explanation:
1. Magnesium slowly reacts with air and forms a layer of magnesium oxide on its surface.
2. The oxide layer hinders burning, so the ribbon is cleaned with sandpaper.

Teacher's Note:
1. Clean metals before experiments to expose fresh metal.
2. The coating is magnesium oxide.

Question 21: A 2 cm long thin ribbon of a metal X was taken and first cleaned with a sandpaper. It was then burnt using a spirit lamp or burner by holding it with a pair of tongs. The ribbon burnt with a dazzling white flame and formed a powder Y which was collected in a watch glass. Which option correctly identifies both X and Y?
(a) X: magnesium; Y: magnesium carbonate
(b) X: aluminium; Y: aluminium oxide
(c) X: magnesium; Y: magnesium oxide
(d) X: iron; Y: iron oxide
Show Answer & Explanation

Answer: (c) X: magnesium; Y: magnesium oxide

Explanation:
1. Only magnesium burns with a dazzling white flame in air.
2. The product is magnesium oxide, a white powder.

Teacher's Note:
1. Dazzling white flame identifies magnesium.
2. Burning in air gives the oxide, not the carbonate.

Question 22: In which of the following, heat energy will be evolved?
(a) Burning of L.P.G.
(b) Dissolution of NH4Cl in water
(c) Electrolysis of water
(d) Decomposition of AgBr in the presence of sunlight
Show Answer & Explanation

Answer: (a) Burning of L.P.G.

Explanation:
1. Burning (combustion) always releases heat.
2. Dissolving NH4Cl, electrolysis and photolysis absorb energy.

Teacher's Note:
1. Combustion is exothermic.
2. Decomposition reactions generally absorb energy.

Question 23: Which of the following are exothermic processes?
(i) Reaction of water with quick lime (ii) Dilution of an acid (iii) Evaporation of water (iv) Sublimation of camphor (crystals)
(a) (i) and (ii)
(b) (ii) and (iii)
(c) (i) and (iv)
(d) (iii) and (iv)
Show Answer & Explanation

Answer: (a) (i) and (ii)

Explanation:
1. Slaking of lime and dilution of an acid release heat.
2. Evaporation and sublimation absorb heat.

Teacher's Note:
1. A warm test tube means exothermic.
2. Changing into a gas absorbs heat.

Question 24: Which of the following is (are) an endothermic process(es)?
(i) Dilution of sulphuric acid (ii) Sublimation of dry ice (iii) Condensation of water vapours (iv) Evaporation of water
(a) (i) and (iii)
(b) (ii) only
(c) (iii) only
(d) (ii) and (iv)
Show Answer & Explanation

Answer: (d) (ii) and (iv)

Explanation:
1. Changing from solid or liquid to gas absorbs heat, so (ii) and (iv) are endothermic.
2. Dilution of acid and condensation release heat.

Teacher's Note:
1. Going to a gas needs heat.
2. Coming from a gas releases heat.

Question 25: Which of the following reactions is an endothermic reaction?
(a) Burning of coal
(b) Decomposition of vegetable matter into compost
(c) Process of respiration
(d) Decomposition of calcium carbonate to form quick lime and carbon dioxide
Show Answer & Explanation

Answer: (d) Decomposition of calcium carbonate to form quick lime and carbon dioxide

Explanation:
1. Heat must be supplied continuously to decompose CaCO3.
2. Burning, composting and respiration all release heat.

Teacher's Note:
1. Endothermic reactions absorb heat.
2. Thermal decompositions are usually endothermic.

Question 26: Which of the following is an endothermic reaction?
(a) Combination of carbon and oxygen to form carbon monoxide
(b) Combination of nitrogen and oxygen to form nitrogen monoxide
(c) Combination of glucose and oxygen to form carbon dioxide and water
(d) Combination of zinc and hydrochloric acid to form zinc chloride and hydrogen
Show Answer & Explanation

Answer: (b) Combination of nitrogen and oxygen to form nitrogen monoxide

Explanation:
1. N2 + O2 → 2NO absorbs heat, so it is endothermic.
2. Burning carbon, respiration of glucose and the reaction of zinc with acid all release heat.

Teacher's Note:
1. Reactions that need very high temperatures to begin are often endothermic.
2. Compare with the exothermic ones.

Question 27: The oxidation reaction which produces heat and light is called
(a) endothermic
(b) photochemical
(c) exothermic
(d) combustion
Show Answer & Explanation

Answer: (d) combustion

Explanation:
1. Combustion is oxidation of a substance with the release of heat and light.
2. Exothermic only means heat is released.

Teacher's Note:
1. Combustion gives heat and light.
2. All combustion is exothermic.

Question 28: The process of respiration is
(a) oxidation reaction which is endothermic
(b) reduction reaction which is endothermic
(c) combination reaction which is exothermic
(d) oxidation reaction which is exothermic
Show Answer & Explanation

Answer: (d) oxidation reaction which is exothermic

Explanation:
1. In respiration glucose is oxidised: C6H12O6 + 6O2 → 6CO2 + 6H2O + energy.
2. Energy is released, so it is exothermic.

Teacher's Note:
1. Respiration provides energy to cells.
2. It is the reverse of photosynthesis in terms of atoms.

Question 29: The reaction of H2 gas with oxygen gas to form water is an example of
(a) combination reaction
(b) redox reaction
(c) exothermic reaction
(d) all of these reactions
Show Answer & Explanation

Answer: (d) all of these reactions

Explanation:
1. 2H2 + O2 → 2H2O joins two substances into one: combination.
2. Hydrogen gains oxygen and oxygen is reduced: redox. Heat is released: exothermic.

Teacher's Note:
1. A reaction may belong to more than one type.
2. Check each classification separately.

Question 30: In which of the following is heat absorbed generally?
(a) Combination reaction
(b) Decomposition reaction
(c) Displacement reaction
(d) Double displacement reaction
Show Answer & Explanation

Answer: (b) Decomposition reaction

Explanation:
1. Decomposition reactions generally need heat, light or electricity to break bonds.
2. Combination reactions are generally exothermic.

Teacher's Note:
1. Breaking bonds needs energy.
2. Exceptions exist, but this is the general rule.

Assertion–Reason Questions

Question 31:
Assertion (A): Quicklime reacts vigorously with water releasing a large amount of heat.
Reason (R): The above chemical reaction is an exothermic reaction.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is not the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Show Answer & Explanation

Answer: (a) Both A and R are true, and R is the correct explanation of A.

Explanation:
1. Both statements are true.
2. Release of heat is the characteristic of an exothermic reaction, so R explains A.

Teacher's Note:
1. Exothermic means heat is released.
2. Slaked lime is formed.

Question 32:
Assertion (A): Photosynthesis is considered an endothermic reaction.
Reason (R): Energy gets released in the process of photosynthesis.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is not the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Show Answer & Explanation

Answer: (c) A is true, but R is false.

Explanation:
1. A is true: sunlight energy is absorbed by the green plants.
2. R is false: energy is absorbed, not released.

Teacher's Note:
1. Absorbed versus released is the whole point.
2. Respiration releases energy.

Question 33:
Assertion (A): Decomposition of vegetable matter into compost is an endothermic reaction.
Reason (R): Decomposition reaction involves breakdown of a single reactant into simpler products.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is not the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Show Answer & Explanation

Answer: (d) A is false, but R is true.

Explanation:
1. A is false: composting releases heat, so it is exothermic.
2. R is a correct statement.

Teacher's Note:
1. Composting makes the heap warm.
2. Not all decompositions are endothermic.

Question 34:
Assertion (A): Burning of natural gas is an endothermic process.
Reason (R): Methane gas combines with oxygen to produce carbon dioxide and water.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is not the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Show Answer & Explanation

Answer: (d) A is false, but R is true.

Explanation:
1. A is false: burning (combustion) is exothermic.
2. R is true: CH4 + 2O2 → CO2 + 2H2O.

Teacher's Note:
1. All combustion reactions release heat.
2. Natural gas is mainly methane.

Question 35:
Assertion (A): The reaction MnO2 + 4HCl → MnCl2 + 2H2O + Cl2 is an example of a redox reaction.
Reason (R): In this reaction HCl is reduced to Cl2 whereas MnO2 is oxidised to MnCl2.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is not the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Show Answer & Explanation

Answer: (c) A is true, but R is false.

Explanation:
1. A is true: MnO2 loses oxygen and HCl loses hydrogen.
2. R reverses the roles; HCl is oxidised and MnO2 is reduced, so R is false.

Teacher's Note:
1. MnO₂ is the oxidising agent.
2. Chlorine is oxidised from HCl.

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Multiple Choice Questions (MCQs) for Class 10 Science Chapter 01 Chemical Reactions and Equations

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