CBSE Class 10 Chemistry Chemical Reactions and Equations MCQs Set 20

Download CBSE MCQs for Class 10 Chemistry: Chemical Reactions and Equations

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

Chapter-wise Objective Questions: Chemical Reactions and Equations

Access the complete set of multiple-choice questions for Chemical Reactions and Equations below. This focused format allows students to isolate specific topics for thorough review and uninterrupted practice alongside official CBSE textbooks.

Multiple Choice Questions

Question 1: What amount of \( \ce{CO2} \) is evolved when 50 g of \( \ce{CaCO3} \) is strongly heated?
(a) 0.25 mol
(b) 0.35 mol
(c) 0.45 mol
(d) 0.5 mol
Show Answer & Explanation

Answer: (d) 0.5 mol

Explanation:
1. Molar mass of \( \ce{CaCO3} \) = 40 + 12 + 48 = 100 g per mol, so 50 g = 0.5 mol.
2. \( \ce{CaCO3 -> CaO + CO2} \) gives 1 mol of \( \ce{CO2} \) per mole of \( \ce{CaCO3} \).
3. So 0.5 mol of \( \ce{CO2} \) is evolved.

Teacher's Note:
1. Use mole ratios from the balanced equation.
2. 1 mol of \( \ce{CaCO3} \) gives 1 mol of \( \ce{CO2} \).

Question 2: What happens when a copper rod is dipped in iron sulphate solution?
(a) Copper displaces iron
(b) Blue colour of copper sulphate solution is obtained
(c) No reaction takes place
(d) Reaction is exothermic
Show Answer & Explanation

Answer: (c) No reaction takes place

Explanation:
1. Copper is less reactive than iron, so it cannot displace iron from iron sulphate.
2. No reaction takes place.

Teacher's Note:
1. A less reactive metal cannot displace a more reactive one.
2. Compare positions in the reactivity series.

Question 3: \( \ce{AgNO3(aq) + NaCl(aq) -> AgCl(s) + NaNO3(aq)} \). The above reaction is a
(a) precipitation reaction
(b) combination reaction
(c) decomposition reaction
(d) both precipitation and double displacement reaction
Show Answer & Explanation

Answer: (d) both precipitation and double displacement reaction

Explanation:
1. Insoluble silver chloride forms, so it is a precipitation reaction.
2. Silver and sodium exchange anions, so it is also a double displacement reaction.

Teacher's Note:
1. A precipitation reaction is a type of double displacement reaction.
2. Silver chloride is a white solid.

Question 4: \( \ce{Zn + H2SO4} \) (dilute) \( \ce{-> ZnSO4 + H2} \). The above reaction is
(a) a decomposition reaction
(b) a single displacement reaction
(c) a neutralisation reaction
(d) a precipitation reaction
Show Answer & Explanation

Answer: (b) a single displacement reaction

Explanation:
1. Zinc displaces hydrogen from sulphuric acid.
2. One element replaces another, so it is single displacement.

Teacher's Note:
1. Metal + acid is displacement.
2. Hydrogen gas is evolved.

Question 5: The reaction \( \ce{CuO + H2 -> H2O + Cu} \) is an example of
(a) redox reaction
(b) decomposition reaction
(c) neutralisation
(d) analysis reaction
Show Answer & Explanation

Answer: (a) redox reaction

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

Teacher's Note:
1. Oxidation and reduction occur together.
2. Black copper oxide turns reddish-brown.

Question 6: When a chemical species loses one or more electrons, it is said to have been
(a) oxidised
(b) reduced
(c) remain unchanged
(d) hydrolysed
Show Answer & Explanation

Answer: (a) oxidised

Explanation:
1. Loss of electrons is oxidation.
2. Gain of electrons is reduction.

Teacher's Note:
1. Remember OIL RIG: oxidation is loss, reduction is gain.
2. This is the electron definition.

Question 7: Combustion can be considered as
(a) oxidation
(b) reduction
(c) decomposition
(d) dehydration
Show Answer & Explanation

Answer: (a) oxidation

Explanation:
1. In combustion a substance combines with oxygen, which is oxidation.
2. It also gives out heat and light.

Teacher's Note:
1. Gain of oxygen is oxidation.
2. Rusting and respiration are slow oxidations.

Question 8: Which of the following is a redox reaction?
(a) \( \ce{CaCO3 -> CaO + CO2} \)
(b) \( \ce{H2 + Cl2 -> 2HCl} \)
(c) \( \ce{CaO + 2HCl -> CaCl2 + H2O} \)
(d) \( \ce{NaOH + HCl -> NaCl + H2O} \)
Show Answer & Explanation

Answer: (b) \( \ce{H2 + Cl2 -> 2HCl} \)

Explanation:
1. In \( \ce{H2 + Cl2 -> 2HCl} \) the oxidation number of hydrogen rises from 0 to +1 and that of chlorine falls from 0 to -1.
2. The other reactions involve no change in oxidation numbers.

Teacher's Note:
1. A redox reaction has a change in oxidation numbers.
2. Neutralisation is not a redox reaction.

Question 9: Which of the following statements is incorrect?
(a) In oxidation, oxygen is added to a substance
(b) In reduction, hydrogen is added to a substance
(c) An oxidising agent is oxidised
(d) A reducing agent is oxidised
Show Answer & Explanation

Answer: (c) An oxidising agent is oxidised

Explanation:
1. An oxidising agent oxidises another substance and is itself reduced.
2. So statement (c) is incorrect.

Teacher's Note:
1. Oxidising agent gets reduced and reducing agent gets oxidised.
2. The other statements are correct.

Question 10: Which of the following statements about the reaction \( \ce{ZnO + CO -> Zn + CO2} \) is correct?
(a) ZnO is being oxidised
(b) CO is being reduced
(c) \( \ce{CO2} \) is being oxidised
(d) ZnO is being reduced
Show Answer & Explanation

Answer: (d) ZnO is being reduced

Explanation:
1. ZnO loses oxygen, so it is reduced.
2. CO gains oxygen to become \( \ce{CO2} \), so CO is oxidised.

Teacher's Note:
1. Loss of oxygen is reduction.
2. \( \ce{CO2} \) is just a product.

Question 11: 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 substance that gets oxidised itself brings about the reduction of the other substance.
2. Such a substance is the reducing agent.

Teacher's Note:
1. Reducing agent loses electrons and is itself oxidised.
2. Oxidising agent is itself reduced.

Question 12: In the reaction \( \ce{PbO + C -> Pb + CO} \)
(a) PbO is oxidised
(b) C acts as an oxidising agent
(c) C acts as a reducing agent
(d) this reaction does not represent a redox reaction
Show Answer & Explanation

Answer: (c) C acts as a reducing agent

Explanation:
1. Carbon takes oxygen from PbO, so carbon is oxidised and acts as the reducing agent.
2. PbO loses oxygen and is reduced.

Teacher's Note:
1. The reducing agent itself gets oxidised.
2. This is how lead is extracted from its oxide.

Question 13: The following reaction coordinate diagram represents
EnergyReactantsProductsReaction pathway (a) an exothermic reaction
(b) an endothermic reaction
(c) a reaction that is neither endothermic nor exothermic
(d) a reaction in which a catalyst is used
Show Answer & Explanation

Answer: (b) an endothermic reaction

Explanation:
1. In the diagram the products are at a higher energy than the reactants.
2. Energy is absorbed during the reaction, so it is endothermic.

Teacher's Note:
1. Products above reactants means energy absorbed.
2. The hump is the activation energy barrier.

Question 14: The process of oxidation involves
(a) the absorption of hydrogen atoms
(b) the absorption of electrons
(c) the release of electrons
(d) neither absorption nor release of electrons
Show Answer & Explanation

Answer: (c) the release of electrons

Explanation:
1. Oxidation is loss of electrons.
2. Gain of hydrogen is reduction and gain of electrons is reduction.

Teacher's Note:
1. Oxidation is loss of electrons or hydrogen, gain of oxygen.
2. Reduction is the reverse.

Question 15: Rusting of iron is an example of
(a) Reduction
(b) Ionization
(c) Oxidation
(d) Dissociation
Show Answer & Explanation

Answer: (c) Oxidation

Explanation:
1. Iron combines with oxygen and moisture to form rust, iron oxide.
2. Gain of oxygen is oxidation.

Teacher's Note:
1. Rusting is a slow oxidation.
2. It needs both oxygen and water.

Question 16: In the reaction \( \ce{2MnO2 + 4Al -> 3Mn + 2Al2O3} \) the oxidising agent is
(a) \( \ce{MnO2} \)
(b) Al
(c) \( \ce{Al2O3} \)
(d) Mn
Show Answer & Explanation

Answer: (a) \( \ce{MnO2} \)

Explanation:
1. \( \ce{MnO2} \) loses oxygen to aluminium, so it is reduced.
2. The substance that gets reduced is the oxidising agent.

Teacher's Note:
1. Aluminium is the reducing agent here.
2. Oxidising agent is itself reduced.

Question 17: Which of the following does not corrode when exposed to the atmosphere?
(a) Iron
(b) Copper
(c) Gold
(d) Silver
Show Answer & Explanation

Answer: (c) Gold

Explanation:
1. Gold is very unreactive and does not react with air or moisture.
2. Iron rusts, copper turns green and silver turns black.

Teacher's Note:
1. Gold is called a noble metal.
2. Corrosion is a slow attack of air and moisture on a metal.

Question 18: The reaction \( \ce{Zn^2+(aq) + 2e- -> Zn(s)} \) is
(a) oxidation
(b) reduction
(c) redox reaction
(d) none of these
Show Answer & Explanation

Answer: (b) reduction

Explanation:
1. \( \ce{Zn^2+} \) gains two electrons to become zinc atoms.
2. Gain of electrons is reduction.

Teacher's Note:
1. A half reaction shows only oxidation or only reduction.
2. A redox reaction needs both.

Question 19: Consider the reaction \( \ce{Zn + Cu^2+ -> Zn^2+ + Cu} \). With reference to the above, which one of the following is the correct statement?
(a) Zn is reduced to \( \ce{Zn^2+} \)
(b) Zn is oxidised to \( \ce{Zn^2+} \)
(c) \( \ce{Zn^2+} \) is oxidised to Zn
(d) \( \ce{Cu^2+} \) is oxidised to Cu
Show Answer & Explanation

Answer: (b) Zn is oxidised to \( \ce{Zn^2+} \)

Explanation:
1. Zinc loses two electrons to form \( \ce{Zn^2+} \), so zinc is oxidised.
2. \( \ce{Cu^2+} \) gains the electrons and is reduced to copper.

Teacher's Note:
1. Zn is the reducing agent, \( \ce{Cu^2+} \) the oxidising agent.
2. Zn is oxidised and Cu2+ is reduced.

Question 20: In the reaction \( \ce{PCl3 + Cl2 -> PCl5} \)
(a) \( \ce{PCl3} \) is acting as a reductant
(b) \( \ce{Cl2} \) is acting as a reductant
(c) both \( \ce{PCl3} \) and \( \ce{Cl2} \) are acting as reductants
(d) both \( \ce{PCl3} \) and \( \ce{Cl2} \) are acting as oxidants
Show Answer & Explanation

Answer: (a) \( \ce{PCl3} \) is acting as a reductant

Explanation:
1. In \( \ce{PCl3} \) the oxidation number of P is +3 and in \( \ce{PCl5} \) it is +5, so \( \ce{PCl3} \) is oxidised.
2. Chlorine is reduced, so it is the oxidant.

Teacher's Note:
1. The substance oxidised is the reductant.
2. Chlorine gains electrons.

Question 21: The correct formula of rust is
(a) \( \ce{Fe2O3} \)
(b) \( \ce{Fe3O4} \)
(c) \( \ce{Fe2O3.xH2O} \)
(d) \( \ce{Fe3O4.xH2O} \)
Show Answer & Explanation

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

Explanation:
1. Rust is hydrated iron(III) oxide, \( \ce{Fe2O3.xH2O} \).

Teacher's Note:
1. Rust needs air and moisture.
2. Anhydrous \( \ce{Fe2O3} \) is haematite.

Question 22: Antioxidants are
(a) hydrating agents
(b) dehydrating agents
(c) oxidising agents
(d) reducing agents
Show Answer & Explanation

Answer: (d) reducing agents

Explanation:
1. Antioxidants prevent oxidation of food by being oxidised themselves in preference.
2. So they are reducing agents.

Teacher's Note:
1. Antioxidants are added to fats and oils to prevent rancidity.
2. They get oxidised first.

Question 23: The rate of a chemical reaction can be increased by adding a
(a) catalyst
(b) pigment
(c) reactant
(d) product
Show Answer & Explanation

Answer: (a) catalyst

Explanation:
1. A catalyst lowers the activation energy and speeds up the reaction without being used up.
2. Pigments and products do not speed it up.

Teacher's Note:
1. Catalysts are not consumed in the reaction.
2. Enzymes are natural catalysts.

Question 24: Among the following metals, which corrodes negligibly?
(a) Gold
(b) Platinum
(c) Palladium
(d) All of the above
Show Answer & Explanation

Answer: (d) All of the above

Explanation:
1. Gold, platinum and palladium are noble metals that react very little with air and moisture.
2. So all three corrode negligibly.

Teacher's Note:
1. Noble metals do not corrode easily.
2. That is why they are used in jewellery.

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Practice MCQs for Class 10 Chemistry Chemical Reactions and Equations

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