CBSE Class 10 Chemistry Chemical Reactions and Equations MCQs Set 33

Multiple Choice Questions (MCQs) for Class 10 Chemistry: 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.

Practice Chemical Reactions and Equations MCQs for Class 10 Chemistry

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 happens when dilute hydrochloric acid is added to iron filings?
(a) Hydrogen gas and iron chloride are produced
(b) Chlorine gas and iron hydroxide are produced
(c) No reaction takes place
(d) Iron salt and water are produced
Show Answer & Explanation

Answer: (a) Hydrogen gas and iron chloride are produced

Explanation:
1. Iron lies above hydrogen in the reactivity series, so it displaces hydrogen from dilute acid.
2. Fe + 2HCl → FeCl2 + H2, so hydrogen gas and iron(II) chloride are produced.

Teacher's Note:
1. Metal + dilute acid gives salt + hydrogen.
2. Iron forms iron(II) chloride, not iron(III) chloride, with dilute HCl.

Question 2: Which of the following is an example of thermal decomposition?
(a) CaCO3(s) → CaO(s) + CO2(g)
(b) 2HOCl(aq) → O2(g) + 2HCl(g), in sunlight
(c) 2AgCl(s) → 2Ag(s) + Cl2(g), in sunlight
(d) 2H2O(l) → 2H2(g) + O2(g), by electric current
Show Answer & Explanation

Answer: (a) CaCO3(s) → CaO(s) + CO2(g)

Explanation:
1. Heating limestone breaks it into quick lime and carbon dioxide, so it is thermal decomposition.
2. The others are decomposition by light (b, c) and by electricity (d).

Teacher's Note:
1. Thermal decomposition needs heat energy.
2. Photolysis needs light and electrolysis needs electricity.

Question 3: Heat is evolved during
(a) an endothermic reaction
(b) a displacement reaction in every case
(c) a combustion reaction
(d) a decomposition reaction in every case
Show Answer & Explanation

Answer: (c) a combustion reaction

Explanation:
1. Combustion (burning) always gives out heat, so it is exothermic.
2. Endothermic reactions absorb heat, and displacement and decomposition reactions are not always exothermic.

Teacher's Note:
1. Exothermic: heat released. Endothermic: heat absorbed.
2. Respiration is a slow combustion.

Question 4:
Assertion (A): In HClO3 the oxidation number of chlorine is +5.
Reason (R): Oxygen is more electronegative than chlorine.
(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. Let the oxidation number of Cl be x: 1 + x + 3(–2) = 0, so x = +5, and A is true.
2. Oxygen is more electronegative than chlorine and is given –2, which is the basis of this calculation, so R is true and explains A.

Teacher's Note:
1. Oxygen is –2 in most compounds, hydrogen is +1.
2. The sum of oxidation numbers in a neutral molecule is zero.

Question 5: Which one of the following reactions is an example of photodecomposition?
(a) CaCO3(s) → CaO(s) + CO2(g)
(b) NH4Cl(s) → NH3(g) + HCl(g)
(c) 2H2O(l) → 2H2(g) + O2(g)
(d) 2AgCl(s) → 2Ag(s) + Cl2(g)
Show Answer & Explanation

Answer: (d) 2AgCl(s) → 2Ag(s) + Cl2(g)

Explanation:
1. Silver chloride decomposes in sunlight to silver and chlorine, so it is a photodecomposition (it turns grey).
2. The first two need heat and water splitting needs electricity.

Teacher's Note:
1. Silver bromide is used in black and white photography for the same reason.
2. Photodecomposition needs light energy.

Question 6: Oxidation is a process which involves
(a) addition of oxygen
(b) removal of hydrogen
(c) loss of electrons
(d) all of the above
Show Answer & Explanation

Answer: (d) all of the above

Explanation:
1. Oxidation was first defined as gain of oxygen or loss of hydrogen.
2. In the modern definition it is loss of electrons, so all three describe oxidation.

Teacher's Note:
1. Reduction is the opposite in all three ways.
2. Remember: oxidation is loss of electrons, increase in oxidation number.

Question 7: When a chemical species loses one or more electrons, it is said to be
(a) oxidised and it acts as a reducing agent
(b) reduced
(c) decomposed
(d) oxidised and it acts as an oxidising agent
Show Answer & Explanation

Answer: (a) oxidised and it acts as a reducing agent

Explanation:
1. Loss of electrons is oxidation.
2. The species that gets oxidised reduces something else, so it is a reducing agent.

Teacher's Note:
1. OIL RIG: Oxidation Is Loss, Reduction Is Gain.
2. The oxidising agent is the species that gains electrons.

Question 8: In the reaction Zn + FeSO4 → ZnSO4 + Fe, which statement is correct?
(a) Zn is oxidised and Fe2+ is reduced
(b) Zn is reduced and Fe2+ is oxidised
(c) Zn is the oxidising agent
(d) both Zn and Fe are oxidised
Show Answer & Explanation

Answer: (a) Zn is oxidised and Fe2+ is reduced

Explanation:
1. Zinc goes from 0 to +2, so it is oxidised and acts as the reducing agent.
2. Iron goes from +2 to 0, so Fe2+ is reduced.

Teacher's Note:
1. Zinc is more reactive than iron.
2. Zn loses electrons, Fe2+ gains them.

Question 9: The oxidation number of phosphorus in Ba(H2PO2)2 (barium hypophosphite) is
(a) +1
(b) +3
(c) +5
(d) –1
Show Answer & Explanation

Answer: (a) +1

Explanation:
1. Ba is +2, so each H2PO2– ion has charge –1.
2. 2(+1) + x + 2(–2) = –1, so x = +1.

Teacher's Note:
1. Hypophosphorous acid is H3PO2.
2. Always get the charge of the ion first.

Question 10: Which of the following has the highest mass?
(a) 3.011 × 1023 atoms of oxygen
(b) ½ mole of CH4
(c) 10 mL of water
(d) 1 gram atom of carbon
Show Answer & Explanation

Answer: (d) 1 gram atom of carbon

Explanation:
1. 1 gram atom of C = 12 g; ½ mole of CH4 = 0.5 × 16 = 8 g.
2. 10 mL of water = 10 g (density 1 g/mL); 3.011 × 1023 atoms of O = 0.5 mol = 8 g.
3. The largest value is 12 g for carbon.

Teacher's Note:
1. Convert each quantity into grams before comparing.
2. One mole contains 6.022 × 1023 particles.

Question 11: Reactions in which rearrangement of atoms present in the molecules of the reactant occurs are known as
(a) isomerisation
(b) polymerisation
(c) combination
(d) decomposition
Show Answer & Explanation

Answer: (a) isomerisation

Explanation:
1. In an isomerisation reaction the molecule keeps its formula but the atoms are rearranged.
2. Example: ammonium cyanate → urea.

Teacher's Note:
1. Combination joins different substances.
2. Decomposition splits a substance.

Question 12: In the ion-electron method the oxidation and reduction half-reactions are balanced separately and added after equalising the electrons. Consider Cr2O72– + C2O42– + H+ → Cr3+ + CO2 + H2O. The balanced reduction half-reaction is
(a) Cr2O72– + 14H+ + 9e– → Cr3+ + 7H2O
(b) Cr2O72– + 14H+ + 6e– → 2Cr3+ + 7H2O
(c) C2O42– → 2CO2 + 2e–
(d) Cr2O72– + 7H+ + 3e– → 2Cr3+ + 7H2O
Show Answer & Explanation

Answer: (b) Cr2O72– + 14H+ + 6e– → 2Cr3+ + 7H2O

Explanation:
1. Chromium changes from +6 to +3, so two Cr atoms gain 6 electrons.
2. Balancing O with 7 H2O and H with 14 H+ gives Cr2O72– + 14H+ + 6e– → 2Cr3+ + 7H2O (charge +6 on both sides).

Teacher's Note:
1. Balance in this order: atoms other than O and H, then O, then H, then charge.
2. Reduction half-reaction has the electrons on the left.

Question 13:
Assertion (A): White phosphorus reacts with caustic soda to give PH3 and NaH2PO2. This is a disproportionation reaction.
Reason (R): In a disproportionation reaction the same substance acts simultaneously as an oxidising agent and as a reducing agent.
(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. P4 is oxidised to H2PO2– (+1) and reduced to PH3 (–3), so A is true.
2. R is the definition of disproportionation and explains A.

Teacher's Note:
1. Disproportionation needs an intermediate oxidation state.
2. Examples: Cl2 in alkali, H2O2 decomposing.

Question 14: Which of the following is the correct balanced equation for burning magnesium ribbon in carbon dioxide?
(a) 2Mg + CO2 → 2MgO + C
(b) Mg + CO2 → MgO + CO2
(c) Mg + CO2 → MgCO3
(d) Mg + 2CO2 → MgO + C
Show Answer & Explanation

Answer: (a) 2Mg + CO2 → 2MgO + C

Explanation:
1. Magnesium is a strong reducing agent and takes oxygen away from CO2.
2. 2Mg + CO2 → 2MgO + C, which balances Mg, O and C.

Teacher's Note:
1. Magnesium fires cannot be put out with CO2.
2. This is a displacement-type redox reaction.

Question 15: When ammonium chloride is dissolved in water in a beaker, the beaker becomes cold. This is because the dissolution is
(a) exothermic, as it gives out heat
(b) a combination reaction
(c) endothermic, as it absorbs heat from the water and the surroundings
(d) a redox reaction
Show Answer & Explanation

Answer: (c) endothermic, as it absorbs heat from the water and the surroundings

Explanation:
1. Dissolving ammonium chloride absorbs heat from the surroundings.
2. A process that absorbs heat is endothermic, so the beaker feels cold.

Teacher's Note:
1. Exothermic processes feel hot.
2. Cold packs use this effect.

Question 16: Iron nails do not rust when kept in distilled water for a long time because
(a) rusting needs both oxygen (air) and moisture containing dissolved oxygen, and boiled or distilled water has no dissolved air
(b) iron is inert in water
(c) distilled water makes iron heavier
(d) distilled water is an acid
Show Answer & Explanation

Answer: (a) rusting needs both oxygen (air) and moisture containing dissolved oxygen, and boiled or distilled water has no dissolved air

Explanation:
1. Rusting needs oxygen and water together; the dissolved air that supplies oxygen is limited in distilled water (especially if boiled).
2. So the nails do not rust appreciably.

Teacher's Note:
1. In the classic experiment, boiled water and oil on top keep the nails dry of oxygen.
2. Salt water speeds up rusting.

Question 17: Copper does not liberate hydrogen on reacting with dilute sulphuric acid because
(a) sulphuric acid is a base
(b) copper is less reactive than hydrogen
(c) copper forms an oxide layer that prevents any reaction
(d) copper is a gas
Show Answer & Explanation

Answer: (b) copper is less reactive than hydrogen

Explanation:
1. Only metals above hydrogen in the reactivity series can displace it from dilute acids.
2. Copper is below hydrogen, so no reaction takes place.

Teacher's Note:
1. Zn, Fe, Mg and Al react with dilute acids.
2. Copper reacts with hot concentrated H2SO4 giving SO2, not H2.

Question 18: Which types of reactions are represented respectively by (i) CaO + CO2 → CaCO3, (ii) Mg + CuSO4 → MgSO4 + Cu, (iii) CH4 + 2O2 → CO2 + 2H2O and (iv) NH4NO2 → N2 + 2H2O?
(a) combination, decomposition, displacement, combustion
(b) combination, displacement, combustion (oxidation), decomposition
(c) displacement, combination, decomposition, combustion
(d) decomposition, combination, displacement, combustion
Show Answer & Explanation

Answer: (b) combination, displacement, combustion (oxidation), decomposition

Explanation:
1. (i) Two substances give one product: combination.
2. (ii) Mg displaces Cu: displacement. (iii) Burning of methane in oxygen: combustion (oxidation).
3. (iv) One compound gives two products on heating: decomposition.

Teacher's Note:
1. Classify by the number of reactants and products.
2. Combustion is also called burning and is exothermic.

Question 19: Why should a magnesium ribbon be cleaned before burning in air?
(a) to cool it
(b) to remove the layer of magnesium oxide formed on its surface so that the metal can burn
(c) to remove its colour
(d) to make it heavier
Show Answer & Explanation

Answer: (b) to remove the layer of magnesium oxide formed on its surface so that the metal can burn

Explanation:
1. Magnesium reacts slowly with air and its surface is covered by a dull layer of MgO.
2. This layer prevents the metal below from reacting, so it is cleaned with sandpaper.

Teacher's Note:
1. Burning magnesium gives a dazzling white flame.
2. 2Mg + O2 → 2MgO.

Question 20: In Activity 1.7 of NCERT (electrolysis of water), the amount of gas collected in one test tube is double that in the other because
(a) oxygen is lighter
(b) hydrogen is heavier
(c) water contains two parts hydrogen to one part oxygen by volume, and the gas collected at the cathode is hydrogen
(d) the tubes have different sizes
Show Answer & Explanation

Answer: (c) water contains two parts hydrogen to one part oxygen by volume, and the gas collected at the cathode is hydrogen

Explanation:
1. 2H2O → 2H2 + O2 gives hydrogen and oxygen in the volume ratio 2 : 1.
2. The tube with double the volume collects hydrogen at the cathode.

Teacher's Note:
1. The gas with larger volume burns with a pop.
2. Water is made of H and O atoms in the ratio 2 : 1.

Question 21: Which pair of a reaction and its type is correct? (A) KBr(aq) + BaI2(aq) → KI(aq) + BaBr2(s) (B) ZnCO3(s) → ZnO(s) + CO2(g) (C) H2(g) + Cl2(g) → 2HCl(g) (D) Mg(s) + 2HCl(aq) → MgCl2(aq) + H2(g)
(a) A displacement, B combination, C decomposition, D double displacement
(b) A decomposition, B displacement, C double displacement, D combination
(c) A combination, B double displacement, C displacement, D decomposition
(d) A double displacement, B decomposition, C combination, D displacement
Show Answer & Explanation

Answer: (d) A double displacement, B decomposition, C combination, D displacement

Explanation:
1. (A) is a precipitation (double displacement), (B) breaks one compound into two simpler substances, (C) joins two elements and (D) has Mg displacing H.
2. So the first option is correct (the balanced (A) is 2KBr + BaI2 → 2KI + BaBr2).

Teacher's Note:
1. Count the number of reactants and products first.
2. Check whether ions are exchanged.

Question 22: What is the sum of all the coefficients when the equation NH3 + O2 → NO + H2O is balanced using the smallest whole numbers?
(a) 20
(b) 18
(c) 17
(d) 19
Show Answer & Explanation

Answer: (d) 19

Explanation:
1. Balance the atoms of each element in turn.
2. The balanced equation is 4NH3 + 5O2 → 4NO + 6H2O.
3. The coefficients add up to 4+5+4+6 = 19.

Teacher's Note:
1. Never change a subscript while balancing, only the coefficients.
2. Check every element on both sides at the end.

Question 23: What is the sum of all the coefficients when the equation Al2(SO4)3 + NaOH → Al(OH)3 + Na2SO4 is balanced using the smallest whole numbers?
(a) 12
(b) 14
(c) 11
(d) 15
Show Answer & Explanation

Answer: (a) 12

Explanation:
1. Balance the atoms of each element in turn.
2. The balanced equation is Al2(SO4)3 + 6NaOH → 2Al(OH)3 + 3Na2SO4.
3. The coefficients add up to 1+6+2+3 = 12.

Teacher's Note:
1. Never change a subscript while balancing, only the coefficients.
2. Check every element on both sides at the end.

Free study material for Science

Multiple Choice Questions (MCQs) for Class 10 Chemistry Chemical Reactions and Equations

About Chemical Reactions and Equations MCQs for Class 10 Chemistry

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

How to Verify Your MCQ Answers

Each question includes structured solution keys mapped directly to standard CBSE textbooks, helping students evaluate their reasoning and correct mistakes early in their revision.

Enhance Speed with Online MCQ Tests

Explore our broader library of printable assignments, chapter notes, and mock tests designed to support continuous revision and secure higher marks in CBSE assessments.

FAQs

Where can I access latest CBSE Class 10 Chemistry Chemical Reactions and Equations MCQs Set 33?

You can get most exhaustive CBSE Class 10 Chemistry Chemical Reactions and Equations MCQs Set 33 for free on StudiesToday.com. These MCQs for Class 10 Chemistry are updated for the 2026-27 academic session as per CBSE examination standards.

Are Assertion-Reasoning and Case-Study MCQs included in the Chemistry Class 10 material?

Yes, our CBSE Class 10 Chemistry Chemical Reactions and Equations MCQs Set 33 include the latest type of questions, such as Assertion-Reasoning and Case-based MCQs. 50% of the CBSE paper is now competency-based.

How do practicing Chemistry MCQs help in scoring full marks in Class 10 exams?

By solving our CBSE Class 10 Chemistry Chemical Reactions and Equations MCQs Set 33, Class 10 students can improve their accuracy and speed which is important as objective questions provide a chance to secure 100% marks in the Chemistry.

Do you provide answers and explanations for CBSE Class 10 Chemistry Chemical Reactions and Equations MCQs Set 33?

Yes, Chemistry MCQs for Class 10 have answer key and brief explanations to help students understand logic behind the correct option as its important for 2026 competency-focused CBSE exams.

Can I practice these Chemistry Class 10 MCQs online?

Yes, you can also access online interactive tests for CBSE Class 10 Chemistry Chemical Reactions and Equations MCQs Set 33 on StudiesToday.com as they provide instant answers and score to help you track your progress in Chemistry.