CBSE Class 10 Science Chemical Reactions and Equations MCQs Set 10

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

Review structured MCQ sets for Class 10 Science Chapter 01 Chemical Reactions and Equations. Built according to official CBSE guidelines, these downloadable questions support daily revision and core concept reinforcement.

Practice Chapter 01 Chemical Reactions and Equations MCQs for Class 10 Science

View or download the dedicated Chapter 01 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 Science evaluations.

Practise 35 MCQs with answers on the types of chemical reactions in CBSE Class 10 Science Chapter 1. The questions deal with combination, decomposition (thermal, photolytic and electrolytic), double displacement and precipitation reactions, with an explanation for each answer.

Multiple Choice Questions

Question 1: Which of the following is a decomposition reaction?
(a) 2HgO → 2Hg + O2 (heat)
(b) CaCO3 → CaO + CO2 (heat)
(c) 2H2O → 2H2 + O2 (electrolysis)
(d) All of these
Show Answer & Explanation

Answer: (d) All of these

Explanation:
1. In each reaction a single compound breaks down into simpler substances.
2. HgO, CaCO3 and H2O each give simpler products, so all three are decomposition reactions.

Teacher's Note:
1. One reactant and several products is the pattern.
2. The energy source may be heat, light or electricity.

Question 2: Which of the following reactions involves the combination of two elements?
(a) CaO + CO2 → CaCO3
(b) 4Na + O2 → 2Na2O
(c) NH3 + HCl → NH4Cl
(d) SO3 + H2O → H2SO4
Show Answer & Explanation

Answer: (b) 4Na + O2 → 2Na2O

Explanation:
1. In (b) sodium and oxygen, both elements, combine to form sodium oxide.
2. In the other options at least one reactant is a compound.

Teacher's Note:
1. All four are combination reactions, but only (b) uses two elements.
2. Read the question for the word elements.

Question 3: Which of the following are combination reactions?
(i) 2KClO3 → 2KCl + 3O2
(ii) MgO + H2O → Mg(OH)2
(iii) 4Al + 3O2 → 2Al2O3
(iv) Zn + FeSO4 → ZnSO4 + Fe
(a) (i) and (iii)
(b) (iii) and (iv)
(c) (ii) and (iv)
(d) (ii) and (iii)
Show Answer & Explanation

Answer: (d) (ii) and (iii)

Explanation:
1. In (ii) and (iii) two reactants form a single product.
2. (i) is decomposition and (iv) is displacement.

Teacher's Note:
1. A combination reaction has a single product.
2. Check the number of products first.

Question 4: Which of the following reactions represents a combination reaction?
(a) CaO(s) + H2O(l) → Ca(OH)2(aq)
(b) CaCO3(s) → CaO(s) + CO2(g)
(c) Zn(s) + CuSO4(aq) → ZnSO4(aq) + Cu(s)
(d) 2FeSO4(s) → Fe2O3(s) + SO2(g) + SO3(g)
Show Answer & Explanation

Answer: (a) CaO(s) + H2O(l) → Ca(OH)2(aq)

Explanation:
1. In (a) two substances combine to form one product, calcium hydroxide.
2. (b) and (d) are decompositions, and (c) is a displacement.

Teacher's Note:
1. Look for a single product.
2. Quicklime and water give slaked lime.

Question 5: Reaction P: CaO + SO3 → CaSO4. Reaction Q: ZnCO3 → ZnO + CO2. Which reaction is an example of a combination reaction and which of a decomposition reaction?
(a) Both are decomposition reactions
(b) P is decomposition and Q is combination
(c) P is combination and Q is decomposition
(d) Both are combination reactions
Show Answer & Explanation

Answer: (c) P is combination and Q is decomposition

Explanation:
1. In P two compounds join to form one product: combination.
2. In Q one compound splits into two products: decomposition.

Teacher's Note:
1. Count reactants and products.
2. One product means combination; one reactant means decomposition.

Question 6: Which among the following is (are) double displacement reaction(s)?
(i) Pb + CuCl2 → PbCl2 + Cu
(ii) Na2SO4 + BaCl2 → BaSO4 + 2NaCl
(iii) C + O2 → CO2
(iv) CH4 + 2O2 → CO2 + 2H2O
(a) (i) and (iv)
(b) (ii) only
(c) (i) and (ii)
(d) (iii) and (iv)
Show Answer & Explanation

Answer: (b) (ii) only

Explanation:
1. In (ii) Na⁺ and Ba²⁺ exchange their partner ions, forming insoluble BaSO4.
2. (i) is displacement, (iii) combination and (iv) combustion (oxidation).

Teacher's Note:
1. Look for the exchange of ions between two compounds.
2. A white precipitate is a clue.

Question 7: Consider the equations I. Mg + 2HCl → MgCl2 + H2 and II. NaOH + HCl → NaCl + H2O. The correct statement about these equations is
(a) I is a displacement reaction and II is a decomposition reaction
(b) I is a displacement reaction and II is a double displacement reaction
(c) Both I and II are displacement reactions
(d) Both I and II are double displacement reactions
Show Answer & Explanation

Answer: (b) I is a displacement reaction and II is a double displacement reaction

Explanation:
1. In I magnesium replaces hydrogen from HCl: displacement.
2. In II the ions of NaOH and HCl are exchanged: double displacement (neutralisation).

Teacher's Note:
1. One replaced element means displacement.
2. Two exchanged ion pairs mean double displacement.

Question 8: The reaction in which two compounds exchange their ions to form two new compounds is
(a) a displacement reaction
(b) a decomposition reaction
(c) an isomerisation reaction
(d) a double displacement reaction
Show Answer & Explanation

Answer: (d) a double displacement reaction

Explanation:
1. This is the definition of a double displacement reaction.
2. In a displacement reaction only one element is replaced.

Teacher's Note:
1. Think of partner swapping.
2. AB + CD gives AD + CB.

Question 9: Zn + H2SO4(dil) → ZnSO4 + H2↑. The above reaction is
(a) a decomposition reaction
(b) a single displacement reaction
(c) a combination reaction
(d) a synthesis reaction
Show Answer & Explanation

Answer: (b) a single displacement reaction

Explanation:
1. Zinc is more reactive than hydrogen and displaces it from the acid.
2. One element replaces another from a compound, so it is a single displacement reaction.

Teacher's Note:
1. Metal + acid gives salt + hydrogen.
2. This is a displacement reaction.

Question 10: Fe2O3 + 2Al → Al2O3 + 2Fe. The above reaction is an example of a
(a) combination reaction
(b) double displacement reaction
(c) decomposition reaction
(d) displacement reaction
Show Answer & Explanation

Answer: (d) displacement reaction

Explanation:
1. Aluminium is more reactive than iron.
2. It displaces iron from iron(III) oxide, so this is a displacement reaction.

Teacher's Note:
1. A more reactive metal displaces a less reactive one from its compound.
2. A large amount of heat is released.

Question 11: Which among the following is a displacement reaction?
(a) CaO + H2O → Ca(OH)2
(b) MgCO3 → MgO + CO2
(c) Mg + CuSO4 → MgSO4 + Cu
(d) H2 + Cl2 → 2HCl
Show Answer & Explanation

Answer: (c) Mg + CuSO4 → MgSO4 + Cu

Explanation:
1. Magnesium is more reactive than copper and takes its place in the salt.
2. (a) and (d) are combinations, and (b) is a decomposition.

Teacher's Note:
1. Check which metal is more reactive.
2. One element replaces another.

Question 12: Which of the following is a displacement reaction?
(a) MgCO3 → MgO + CO2
(b) 2Na + 2H2O → 2NaOH + H2
(c) 2H2 + O2 → 2H2O
(d) 2Pb(NO3)2 → 2PbO + 4NO2 + O2
Show Answer & Explanation

Answer: (b) 2Na + 2H2O → 2NaOH + H2

Explanation:
1. Sodium displaces hydrogen from water.
2. (a) and (d) are decompositions; (c) is a combination.

Teacher's Note:
1. Metal + water/acid gives displacement of hydrogen.
2. Look for a single element replaced.

Question 13: Example of a displacement reaction is
(a) Fe(s) + CuSO4(aq) → FeSO4(aq) + Cu(s)
(b) C(s) + O2(g) → CO2(g)
(c) 2AgCl(s) → 2Ag(s) + Cl2(g) (sunlight)
(d) BaCl2(aq) + Na2SO4(aq) → BaSO4(s) + 2NaCl(aq)
Show Answer & Explanation

Answer: (a) Fe(s) + CuSO4(aq) → FeSO4(aq) + Cu(s)

Explanation:
1. Iron takes the place of copper in copper sulphate.
2. (b) is combination, (c) decomposition and (d) double displacement.

Teacher's Note:
1. More reactive metal replaces less reactive metal.
2. The nail becomes brown and the solution turns green.

Question 14: When hydrogen sulphide gas is passed through a blue solution of copper sulphate, a black precipitate of copper sulphide is obtained and the sulphuric acid so formed remains in the solution. The reaction is an example of a
(a) combination reaction
(b) displacement reaction
(c) decomposition reaction
(d) double displacement reaction
Show Answer & Explanation

Answer: (d) double displacement reaction

Explanation:
1. CuSO4 + H2S → CuS + H2SO4: Cu²⁺ and H⁺ exchange partners.
2. Two compounds swap ions, so it is a double displacement (precipitation) reaction.

Teacher's Note:
1. Two compounds react to give two new compounds.
2. The black solid is CuS.

Question 15: Example of a double displacement reaction will be
(a) Metal with a salt
(b) Metal with an acid
(c) Metal with metal
(d) Salt with a salt
Show Answer & Explanation

Answer: (d) Salt with a salt

Explanation:
1. In double displacement two compounds exchange ions.
2. A salt with a salt, e.g. BaCl2 with Na2SO4, is such a case.

Teacher's Note:
1. Both reactants must be compounds.
2. A metal in the reactants means displacement.

Question 16: Barium chloride on reacting with ammonium sulphate forms barium sulphate and ammonium chloride. Which of the following correctly represents the type of the reaction involved?
(i) Displacement (ii) Precipitation (iii) Combination (iv) Double displacement
(a) (i) only
(b) (ii) only
(c) (iv) only
(d) (ii) and (iv)
Show Answer & Explanation

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

Explanation:
1. BaCl2 + (NH4)2SO4 → BaSO4 + 2NH4Cl: ions are exchanged, a double displacement reaction.
2. Insoluble BaSO4 separates as a solid, so it is also a precipitation reaction.

Teacher's Note:
1. Many double displacement reactions form a precipitate.
2. Neutralisation does not.

Question 17: Barium chloride solution is added to sodium sulphate solution. Identify the product which represents the solid state.
(a) Barium chloride
(b) Barium sulphate
(c) Sodium chloride
(d) Sodium sulphate
Show Answer & Explanation

Answer: (b) Barium sulphate

Explanation:
1. Na2SO4(aq) + BaCl2(aq) → BaSO4(s) + 2NaCl(aq)
2. Barium sulphate is insoluble and appears as a white precipitate.

Teacher's Note:
1. The (s) symbol marks the precipitate.
2. NaCl stays dissolved.

Question 18: In the double displacement reaction between aqueous potassium iodide and aqueous lead nitrate, a yellow precipitate of lead iodide is formed. While performing the activity if lead nitrate is not available, which of the following can be used in place of lead nitrate?
(a) Lead sulphate (insoluble)
(b) Lead acetate
(c) Ammonium nitrate
(d) Potassium sulphate
Show Answer & Explanation

Answer: (b) Lead acetate

Explanation:
1. A soluble lead salt is needed to supply lead ions in solution.
2. Lead acetate is soluble and gives yellow PbI2; lead sulphate is insoluble and the other two contain no lead.

Teacher's Note:
1. The substitute must contain lead and dissolve in water.
2. Check solubility and composition.

Question 19: In a double displacement reaction such as the reaction between sodium sulphate solution and barium chloride solution:
(A) exchange of atoms takes place (B) exchange of ions takes place (C) a precipitate is produced (D) an insoluble salt is produced. The correct option is
(a) (B) and (D)
(b) (A) and (C)
(c) only (B)
(d) (B), (C) and (D)
Show Answer & Explanation

Answer: (d) (B), (C) and (D)

Explanation:
1. Ions are exchanged, and insoluble BaSO4 forms as a precipitate.
2. So (B), (C) and (D) are all correct.

Teacher's Note:
1. Atoms are not exchanged; ions are.
2. A precipitate is an insoluble salt.

Question 20: The chemical reaction between potassium chloride and silver nitrate is given by KCl + AgNO3 → AgCl + KNO3. What can be inferred from the chemical equation?
(a) Silver nitrate and potassium undergo a combination reaction to form silver chloride and potassium nitrate
(b) Silver nitrate and potassium undergo a decomposition reaction
(c) Silver nitrate and potassium undergo a displacement reaction
(d) Silver nitrate and potassium chloride undergo a double displacement reaction to form silver chloride and potassium nitrate
Show Answer & Explanation

Answer: (d) Silver nitrate and potassium chloride undergo a double displacement reaction to form silver chloride and potassium nitrate

Explanation:
1. Two compounds, KCl and AgNO3, exchange their ions.
2. The result is two new compounds, so it is a double displacement reaction.

Teacher's Note:
1. Insoluble AgCl is a white precipitate.
2. Do not call potassium a reactant by itself.

Question 21: Electrolysis of water is a
(a) combination reaction
(b) decomposition reaction
(c) displacement reaction
(d) none of these
Show Answer & Explanation

Answer: (b) decomposition reaction

Explanation:
1. 2H2O → 2H2 + O2 when electric current is passed.
2. One compound splits into two elements.

Teacher's Note:
1. Decomposition by electricity is electrolysis.
2. Water decomposes into hydrogen and oxygen.

Question 22: When electricity is passed through water, what kind of reaction takes place?
(a) Thermal decomposition
(b) Electrolytic decomposition
(c) Photochemical decomposition
(d) Displacement reaction
Show Answer & Explanation

Answer: (b) Electrolytic decomposition

Explanation:
1. Electrical energy breaks down water into hydrogen and oxygen.
2. Decomposition using electricity is called electrolytic decomposition.

Teacher's Note:
1. Match the type with the energy used.
2. Heat: thermal; light: photolytic; electricity: electrolytic.

Question 23: The reaction which decomposes after the supply of heat is called
(a) thermal decomposition
(b) combination reaction
(c) redox reaction
(d) displacement reaction
Show Answer & Explanation

Answer: (a) thermal decomposition

Explanation:
1. A compound breaks down into simpler substances when heat is supplied.
2. This is thermal decomposition, e.g. CaCO3 → CaO + CO2.

Teacher's Note:
1. Thermal means related to heat.
2. Most decomposition reactions need energy.

Question 24: Which of the following is a decomposition reaction?
(a) NaOH + HCl → NaCl + H2O
(b) NH4CNO → H2NCONH2
(c) 2KClO3 → 2KCl + 3O2
(d) H2 + I2 → 2HI
Show Answer & Explanation

Answer: (c) 2KClO3 → 2KCl + 3O2

Explanation:
1. In (c) a single compound, KClO3, breaks down into KCl and O2.
2. (a) is double displacement, (d) is combination; (b) rearranges atoms in one compound without breaking it into several products.

Teacher's Note:
1. A decomposition reaction has one reactant and more than one product.
2. Check each option for this pattern.

Question 25: 2Pb(NO3)2 → 2PbO + nA + O2. What is nA in the given reaction?
(a) 4NO
(b) 4NO2
(c) 2PbNO2
(d) NO2
Show Answer & Explanation

Answer: (b) 4NO2

Explanation:
1. Nitrogen: 2 Pb(NO3)2 has 4 N atoms; oxygen: 12 atoms on the left.
2. 2 PbO and O2 account for 4 O atoms, so 8 O remain with 4 N, giving 4NO2.

Teacher's Note:
1. Balance nitrogen and oxygen.
2. NO₂ is the brown gas.

Question 26: Which of the reactions is used in black and white photography?
(a) Combination reaction
(b) Decomposition reaction
(c) Displacement reaction
(d) Double displacement reaction
Show Answer & Explanation

Answer: (b) Decomposition reaction

Explanation:
1. Silver bromide in photographic film decomposes in light to give silver.
2. This is a photochemical decomposition reaction.

Teacher's Note:
1. Silver halides are light sensitive.
2. Films are kept away from light.

Question 27: White silver chloride in sunlight turns to
(a) grey
(b) yellow
(c) remain white
(d) red
Show Answer & Explanation

Answer: (a) grey

Explanation:
1. 2AgCl → 2Ag + Cl2 in sunlight.
2. Fine silver particles make it grey.

Teacher's Note:
1. Silver chloride is stored in dark bottles.
2. This is photolytic decomposition.

Question 28: Black and white photography uses
(a) decomposition of silver chloride
(b) decomposition of silver bromide
(c) both
(d) none of these
Show Answer & Explanation

Answer: (c) both

Explanation:
1. Silver chloride and silver bromide are both light sensitive and decompose to silver in light.
2. The silver formed produces the image.

Teacher's Note:
1. Both silver halides are used in photographic films and paper.
2. They are called photosensitive.

Question 29: Silver chloride on exposure to sunlight decomposes into silver and chlorine gas. This property is used in
(a) heat production as enormous energy is released
(b) silver extraction as earth contains silver mainly in silver chloride form
(c) photography as grey silver formed produces an image imprint
(d) none of the above
Show Answer & Explanation

Answer: (c) photography as grey silver formed produces an image imprint

Explanation:
1. The silver formed in light creates a dark image on a film.
2. So the property is used in photography.

Teacher's Note:
1. Photosensitivity is the useful property here.
2. It is not used for heat or extraction.

Question 30: What happens when silver bromide is exposed to sunlight?
(a) Hydrogen gas is formed
(b) Bromine gas is formed
(c) Chlorine gas is formed
(d) Iodine gas is formed
Show Answer & Explanation

Answer: (b) Bromine gas is formed

Explanation:
1. 2AgBr → 2Ag + Br2 in sunlight.
2. Silver metal and bromine are formed.

Teacher's Note:
1. The halogen in the compound is released.
2. Silver bromide has bromine.

Assertion–Reason Questions

Question 31:
Assertion (A): Precipitation reactions produce insoluble salts.
Reason (R): A precipitation reaction is a double displacement 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: (b) Both A and R are true, but R is not the correct explanation of A.

Explanation:
1. Both statements are true.
2. R does not explain A: a precipitation reaction is a special double displacement reaction, but being double displacement does not by itself make the salt insoluble.

Teacher's Note:
1. Not every double displacement reaction forms a precipitate.
2. Neutralisation is an example without one.

Question 32:
Assertion (A): Decomposition reactions are in a sense opposite to combination reactions.
Reason (R): In a decomposition reaction a single reactant breaks down to give two or more 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: (a) Both A and R are true, and R is the correct explanation of A.

Explanation:
1. Both statements are true.
2. Combination joins substances into one, while decomposition splits one into many, so R explains A.

Teacher's Note:
1. Compare the number of reactants and products.
2. They are opposite processes.

Question 33:
Assertion (A): The reaction CO + 2H2 → CH3OH (at 340 atm) is a combination reaction.
Reason (R): It is a combination reaction because CO combines with H2 to form a single compound.
(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. CO and H2 combine to form one compound, methanol.
2. Both are true, and R explains why A is a combination reaction.

Teacher's Note:
1. Identify the number of products.
2. One product from two reactants means combination.

Question 34:
Assertion (A): Silver bromide is kept in coloured bottles.
Reason (R): It decomposes in the presence of light.
(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. Coloured bottles keep light out, preventing the decomposition, so R explains A.

Teacher's Note:
1. Light-sensitive chemicals need dark bottles.
2. Silver halides are used in photography.

Question 35:
Assertion (A): White silver chloride turns grey in sunlight.
Reason (R): Silver is one of the least reactive metals.
(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: (b) Both A and R are true, but R is not the correct explanation of A.

Explanation:
1. Both statements are true.
2. R does not explain why AgCl decomposes in sunlight; the cause is the energy of light.

Teacher's Note:
1. Two true statements need not be linked.
2. Light energy causes the decomposition.

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