CBSE Class 10 Chemistry Chemical Reactions and Equations MCQs Set 24

Chemistry Objective Questions and Answers: Chemical Reactions and Equations

Review structured MCQ sets for Class 10 Chemistry Chemical Reactions and Equations. Built according to official CBSE guidelines, these downloadable questions support daily revision and core concept reinforcement.

Download Chemical Reactions and Equations MCQs with Answers

View or download the dedicated Chemical Reactions and Equations MCQ resource below. Practicing these 50 objective questions regularly builds familiarity with standard exam patterns and helps secure higher marks in final Chemistry evaluations.

Multiple Choice Questions

Question 1: Rusting of iron needs the presence of
(a) air only
(b) water only
(c) both air and water
(d) neither
Show Answer & Explanation

Answer: (c) both air and water

Explanation:
1. Iron rusts when both oxygen (air) and moisture are present.
2. With only one of them rusting does not occur.

Teacher's Note:
1. Think of the two conditions for rust.

Question 2: Rust is chemically
(a) \( \ce{Fe2O3.xH2O} \)
(b) \( \ce{FeO} \)
(c) \( \ce{FeCl3} \)
(d) \( \ce{Fe(OH)2} \)
Show Answer & Explanation

Answer: (a) \( \ce{Fe2O3.xH2O} \)

Explanation:
1. Rust is hydrated iron(III) oxide.

Teacher's Note:
1. It is a hydrated oxide.

Question 3: Formation of \( \ce{NH4Cl} \) from \( \ce{NH3} \) and \( \ce{HCl} \) is a
(a) decomposition reaction
(b) combination reaction
(c) displacement reaction
(d) double displacement reaction
Show Answer & Explanation

Answer: (b) combination reaction

Explanation:
1. Two compounds combine to give one product.

Teacher's Note:
1. One product from two reactants.

Question 4: Respiration is an example of
(a) endothermic reaction
(b) exothermic reaction
(c) photolysis
(d) electrolysis
Show Answer & Explanation

Answer: (b) exothermic reaction

Explanation:
1. Glucose reacts with oxygen and releases energy, so it is exothermic.

Teacher's Note:
1. Energy is liberated.

Question 5: Silver bromide turns grey in sunlight because
(a) it melts
(b) it decomposes into silver and bromine
(c) it gains oxygen
(d) it dissolves
Show Answer & Explanation

Answer: (b) it decomposes into silver and bromine

Explanation:
1. \( \ce{2AgBr -> 2Ag + Br2} \) by photolysis. Silver is grey.

Teacher's Note:
1. Light causes decomposition.

Question 6: Which is a displacement reaction?
(a) \( \ce{CaO + H2O -> Ca(OH)2} \)
(b) \( \ce{Fe + CuSO4 -> FeSO4 + Cu} \)
(c) \( \ce{2H2O -> 2H2 + O2} \)
(d) \( \ce{NaOH + HCl -> NaCl + H2O} \)
Show Answer & Explanation

Answer: (b) \( \ce{Fe + CuSO4 -> FeSO4 + Cu} \)

Explanation:
1. Iron displaces the less reactive copper from copper sulphate.

Teacher's Note:
1. A more reactive metal pushes out a less reactive one.

Question 7: Decomposition of hydrogen peroxide \( \ce{2H2O2 -> 2H2O + O2} \) is accelerated by
(a) oxygen
(b) light
(c) nitrogen
(d) water
Show Answer & Explanation

Answer: (b) light

Explanation:
1. It is a photolytic decomposition, so light speeds it.

Teacher's Note:
1. Photolysis uses light.

Question 8: Brown fumes are seen on heating lead nitrate. The gas is
(a) \( \ce{O2} \)
(b) \( \ce{NO2} \)
(c) \( \ce{CO2} \)
(d) \( \ce{SO2} \)
Show Answer & Explanation

Answer: (b) \( \ce{NO2} \)

Explanation:
1. \( \ce{2Pb(NO3)2 -> 2PbO + 4NO2 + O2} \). Nitrogen dioxide is brown.

Teacher's Note:
1. Brown gas.

Question 9: Burning of magnesium ribbon forms
(a) MgO
(b) \( \ce{MgCO3} \)
(c) \( \ce{Mg(OH)2} \)
(d) \( \ce{MgH2} \)
Show Answer & Explanation

Answer: (a) MgO

Explanation:
1. \( \ce{2Mg + O2 -> 2MgO} \), a white powder, with a dazzling flame.

Teacher's Note:
1. Burning in air means reacting with oxygen.

Question 10: Copper turns green on exposure to moist air because of
(a) \( \ce{CuO} \)
(b) basic copper carbonate
(c) \( \ce{CuCl2} \)
(d) \( \ce{Cu2S} \)
Show Answer & Explanation

Answer: (b) basic copper carbonate

Explanation:
1. Copper forms \( \ce{CuCO3.Cu(OH)2} \) with moist carbon dioxide.

Teacher's Note:
1. Green coating is a basic carbonate.

Question 11: Silver articles turn black in air due to formation of
(a) \( \ce{Ag2O} \)
(b) \( \ce{AgCl} \)
(c) \( \ce{Ag2S} \)
(d) \( \ce{AgNO3} \)
Show Answer & Explanation

Answer: (c) \( \ce{Ag2S} \)

Explanation:
1. Silver reacts with \( \ce{H2S} \) in air giving black silver sulphide.

Teacher's Note:
1. Think of hydrogen sulphide.

Question 12: Which is an example of a double displacement reaction?
(a) \( \ce{Na2SO4 + BaCl2 -> BaSO4 + 2NaCl} \)
(b) \( \ce{2Mg + O2 -> 2MgO} \)
(c) \( \ce{2HgO -> 2Hg + O2} \)
(d) \( \ce{Zn + H2SO4 -> ZnSO4 + H2} \)
Show Answer & Explanation

Answer: (a) \( \ce{Na2SO4 + BaCl2 -> BaSO4 + 2NaCl} \)

Explanation:
1. Ions exchange partners and a white precipitate of \( \ce{BaSO4} \) forms.

Teacher's Note:
1. Exchange of ions.

Question 13: In an electrolysis of water the volume ratio of hydrogen to oxygen is
(a) 1:2
(b) 2:1
(c) 1:1
(d) 3:1
Show Answer & Explanation

Answer: (b) 2:1

Explanation:
1. \( \ce{2H2O -> 2H2 + O2} \), so hydrogen is twice oxygen by volume.

Teacher's Note:
1. Use the balanced equation.

Question 14: Heating ferrous sulphate crystals first gives a
(a) black residue
(b) green colour change to white, then a reddish brown solid
(c) blue solid
(d) no change
Show Answer & Explanation

Answer: (b) green colour change to white, then a reddish brown solid

Explanation:
1. Green crystals lose water and turn white, then give brown \( \ce{Fe2O3} \) with \( \ce{SO2} \) and \( \ce{SO3} \).

Teacher's Note:
1. Colour sequence of crystals.

Question 15: A chemical equation is balanced to obey
(a) law of definite proportions
(b) law of conservation of mass
(c) Avogadro law
(d) Boyle law
Show Answer & Explanation

Answer: (b) law of conservation of mass

Explanation:
1. Atoms are neither created nor destroyed, so both sides must have equal atoms.

Teacher's Note:
1. Mass is conserved.

Question 16: Which of these is an oxidation?
(a) gain of hydrogen
(b) loss of oxygen
(c) gain of oxygen
(d) gain of electrons
Show Answer & Explanation

Answer: (c) gain of oxygen

Explanation:
1. Gain of oxygen (or loss of hydrogen or electrons) is oxidation.

Teacher's Note:
1. Oxidation is gain of oxygen.

Question 17: Quicklime reacting with water is
(a) endothermic
(b) exothermic
(c) a decomposition
(d) a displacement
Show Answer & Explanation

Answer: (b) exothermic

Explanation:
1. \( \ce{CaO + H2O -> Ca(OH)2} \) releases a lot of heat.

Teacher's Note:
1. The beaker becomes hot.

Question 18: Which of the following is a thermal decomposition?
(a) \( \ce{2Pb(NO3)2 -> 2PbO + 4NO2 + O2} \)
(b) \( \ce{H2 + Cl2 -> 2HCl} \)
(c) \( \ce{Zn + 2HCl -> ZnCl2 + H2} \)
(d) \( \ce{NaOH + HCl -> NaCl + H2O} \)
Show Answer & Explanation

Answer: (a) \( \ce{2Pb(NO3)2 -> 2PbO + 4NO2 + O2} \)

Explanation:
1. One compound breaks into several substances on heating.

Teacher's Note:
1. Heat splits one compound.

Question 19: In \( \ce{CuO + H2 -> Cu + H2O} \) the reducing agent is
(a) CuO
(b) \( \ce{H2} \)
(c) Cu
(d) \( \ce{H2O} \)
Show Answer & Explanation

Answer: (b) \( \ce{H2} \)

Explanation:
1. Hydrogen removes oxygen from CuO, so it is the reducing agent (and is itself oxidised).

Teacher's Note:
1. The substance that is oxidised.

Question 20: Hydrogen gas burns with
(a) a pop sound
(b) a green flame
(c) no flame
(d) a yellow smoke
Show Answer & Explanation

Answer: (a) a pop sound

Explanation:
1. Hydrogen burns with a pop when a flame is brought near.

Teacher's Note:
1. Test for hydrogen.

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Chemical Reactions and Equations Objective Questions & Solutions for Class 10 Chemistry

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Concept Clarification for Chemical Reactions and Equations

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FAQs

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