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Class 10 Science Chapter 1 Chemical Reactions and Equations MCQs (Set 1)

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Class 10 Science Chapter 1 MCQs (Set 1) | Chemical Reactions and Equations

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Section A: Activity & Diagram-Based Questions

1. A student performs the combustion of a magnesium ribbon as shown in the experimental setup below:
Burning of Magnesium Ribbon
Why is the magnesium ribbon rubbed with sandpaper before ignition, and what is the nature of the residue collected in the watch-glass?
2. In an activity, dilute sulphuric acid is poured onto zinc granules contained in a conical flask:
Action of dilute sulphuric acid on zinc
Which observations confirm that a chemical reaction has taken place in the flask?
3. Look at the setup below where water is added to calcium oxide in a glass beaker:
Formation of slaked lime
When a hand touches the beaker from the outside during the reaction, it feels hot. What type of reaction is this?
4. A boiling tube containing green ferrous sulphate crystals is heated over a burner flame as illustrated:
Heating of Ferrous Sulphate Crystals
What are the correct color change and the characteristic smell of the gases evolved?
5. A student heats 2 g of dry lead nitrate powder in a boiling tube as shown:
Heating of Lead Nitrate
What observation confirms thermal decomposition in this experiment?
6. Study the apparatus for the electrolytic decomposition of acidified water:
Electrolysis of Water Setup
Why is the volume of gas collected in the test tube at the cathode double that at the anode?
7. In Activity 1.8, white silver chloride is placed in a china dish under direct sunlight:
Decomposition of Silver Chloride
What causes the white compound to turn grey after a few minutes?
8. Clean iron nails are suspended in a test tube containing blue copper sulphate solution:
Displacement of Copper by Iron
Displacement of Copper by Iron
What changes are observed in the color of the solution and the iron nails after 20 minutes?

Section B: Assertion & Reasoning (CBSE Pattern)

9. Assertion (A): Calcium oxide reacts vigorously with water to form slaked lime, releasing a large amount of heat.
Reason (R): The reaction between quicklime and water is a combination as well as an exothermic reaction.
10. Assertion (A): Respiration is considered an exothermic chemical reaction.
Reason (R): Photosynthesis in green plants absorbs solar energy to synthesize glucose from carbon dioxide and water.
11. Assertion (A): Silver chloride powder is stored in dark amber-colored bottles in chemical laboratories.
Reason (R): Silver chloride reacts with air at room temperature to form toxic chlorine gas without requiring light.
12. Assertion (A): A skeletal chemical equation is always balanced in mass according to the law of conservation of mass.
Reason (R): In a balanced chemical equation, the total number of atoms of each element remains identical on both reactant and product sides.
13. Assertion (A): Bags of potato chips are flushed with nitrogen gas during industrial packaging.
Reason (R): Nitrogen is an unreactive antioxidant gas that prevents oxidative rancidity of fats and oils.
14. Assertion (A): The reaction of copper oxide with hydrogen gas to yield copper and water is a redox reaction.
Reason (R): The substance gaining oxygen is oxidised, while the substance losing oxygen is reduced.
15. Assertion (A): Rusting of iron is an example of an endothermic displacement reaction.
Reason (R): Iron reacts slowly with moisture and oxygen in the air to form hydrated iron(III) oxide.

Section C: Matching & Tabular Competencies

16. Match the chemical reactions in Column I with their correct reaction classifications in Column II:
Column I (Chemical Equation) Column II (Type of Reaction)
(A) 2H₂ + O₂ → 2H₂O(1) Thermal Decomposition
(B) CaCO₃ → CaO + CO₂(2) Displacement Reaction
(C) Zn + CuSO₄ → ZnSO₄ + Cu(3) Double Displacement Reaction
(D) Na₂SO₄ + BaCl₂ → BaSO₄ + 2NaCl(4) Combination Reaction
17. Match the industrial compound in Column I with its correct chemical formula and usage in Column II:
Column I (Common Name) Column II (Formula & Application)
(A) Quicklime(1) CaO; used in cement manufacture
(B) Slaked lime(2) Ca(OH)₂; used for whitewashing walls
(C) Limestone / Marble(3) CaCO₃; provides shiny finish to walls
(D) Green vitriol crystals(4) FeSO₄·7H₂O; yields ferric oxide on heating
18. Match the metal in Column I with the distinctive color of its corrosion product in Column II:
Column I (Metal) Column II (Corrosion Product Coating)
(A) Iron(1) Black coating
(B) Silver(2) Reddish-brown flaky powder
(C) Copper(3) Dull green layer

Section D: Balancing & Stoichiometric Coefficients

19. In the balanced equation: a Fe(s) + b H₂O(g) → c Fe₃O₄(s) + d H₂(g), what are the values of the stoichiometric coefficients a, b, c, and d?
20. What are the values of coefficients x, y, and z required to balance the thermal decomposition of lead nitrate: x Pb(NO₃)₂ → y PbO + z NO₂ + O₂?
21. In the chemical equation for photosynthesis: a CO₂(aq) + b H₂O(l) → C₆H₁₂O₆(aq) + c O₂(aq) + d H₂O(l), what are the values of a, b, and c?

Section E: Comprehensive Concept & Competency Practice

22. When lead nitrate solution is mixed with potassium iodide solution in a test tube (Activity 1.2), a precipitate forms. What is the color and formula of this precipitate?
23. Walls whitewashed with slaked lime solution develop a shiny, lustrous finish after two to three days. Which compound is formed on the wall surface?
24. Which of the following reactions is used in black-and-white photography?
25. When barium hydroxide is mixed with ammonium chloride in a test tube, the bottom of the vessel becomes freezing cold. What type of reaction is this?
26. In the reaction: MnO₂ + 4HCl → MnCl₂ + 2H₂O + Cl₂, which substance acts as the reducing agent?
27. A shiny brown element ‘X’ on heating in air in a china dish becomes coated with a black compound ‘Y’. What are X and Y?
28. Which of the following represents a precipitation double displacement reaction?
29. What happens when dilute hydrochloric acid is added to iron filings in a beaker?
30. In the redox reaction: 2PbO(s) + C(s) → 2Pb(s) + CO₂(g), which statement is correct?
31. What state symbol notation is used to represent a reactant or product dissolved in water as a solution?
32. The decomposition of vegetable matter into organic compost is an example of which type of reaction?
33. Why is black copper oxide coating converted back to shiny brown copper when hydrogen gas is passed over heated CuO?
34. Which of the following metals can displace copper from an aqueous solution of copper sulphate?
35. Which of the following is an example of a thermal decomposition reaction used in the manufacturing of cement?
36. What is the fundamental law of nature that mandates balancing of all chemical equations?
37. In the reaction ZnO + C → Zn + CO, what is the oxidizing agent?
38. Why are airtight containers recommended for storing fried food items containing oils and fats?
39. Which of the following represents a balanced displacement reaction involving silver recovery in metallurgical refining?
40. In which of the following reactions does a combination reaction occur between two elements?
41. Why is the reaction: Fe₂O₃ + 2Al → Al₂O₃ + 2Fe categorized as a displacement reaction?
42. What is the coefficient of HCl when the following equation is balanced: Al(OH)₃ + HCl → AlCl₃ + H₂O?
43. When sodium metal reacts with cold water, which products are formed?
44. Which of the following is NOT an indicator that a chemical change has taken place?
45. What happens when hydrogen sulphide gas burns in air?
46. In the balanced equation: 2HNO₃ + Ca(OH)₂ → Ca(NO₃)₂ + x H₂O, what is the value of x?
47. What occurs when sodium hydroxide solution reacts with dilute hydrochloric acid?
48. Why is respiration classified as a combustion-like exothermic process in humans?
49. What type of reaction is represented by: 2KClO₃ → 2KCl + 3O₂ in the presence of heat?
50. Which observation proves that a chemical reaction occurs when potassium iodide reacts with lead nitrate?

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