20 MCQs based on the chapter "Chemical Reactions and Equations" (Class 10, NCERT-based), without answers:
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A chemical reaction involves:
- (a) Breaking of old bonds
- (b) Formation of new bonds
- (c) Both (a) and (b)
- (d) No bond changes
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Which of the following is a physical change?
- (a) Rusting of iron
- (b) Melting of ice
- (c) Burning of paper
- (d) Cooking of food
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What type of reaction is represented by:
- (a) Combination
- (b) Decomposition
- (c) Displacement
- (d) Double displacement
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Which of the following is an example of an exothermic reaction?
- (a) Photosynthesis
- (b) Evaporation of water
- (c) Respiration
- (d) Boiling of water
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Which gas is evolved when zinc reacts with dilute sulphuric acid?
- (a) Oxygen
- (b) Nitrogen
- (c) Hydrogen
- (d) Chlorine
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Which of the following is not a sign of a chemical reaction?
- (a) Change in color
- (b) Evolution of gas
- (c) Change in shape
- (d) Formation of a precipitate
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The rusting of iron is an example of:
- (a) Combination reaction
- (b) Decomposition reaction
- (c) Redox reaction
- (d) Displacement reaction
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Which of the following reactions is a double displacement reaction?
- (a) Zn + H₂SO₄ → ZnSO₄ + H₂
- (b) NaOH + HCl → NaCl + H₂O
- (c) AgNO₃ + NaCl → AgCl + NaNO₃
- (d) 2H₂ + O₂ → 2H₂O
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Which of these is used as an antacid?
- (a) NaCl
- (b) CaCO₃
- (c) Mg(OH)₂
- (d) HCl
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The process of depositing a thin layer of zinc on iron is called:
- (a) Alloying
- (b) Rusting
- (c) Galvanization
- (d) Amalgamation
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Which of the following represents a balanced chemical equation?
- (a) H₂ + Cl₂ → HCl
- (b) H₂ + Cl₂ → 2HCl
- (c) 2H₂ + O₂ → H₂O
- (d) Fe + O₂ → Fe₂O₃
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The reaction between lead nitrate and potassium iodide is:
- (a) Neutralization reaction
- (b) Displacement reaction
- (c) Combination reaction
- (d) Precipitation reaction
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A chemical equation is said to be balanced when:
- (a) Reactants equal products in number
- (b) Mass of reactants = mass of products
- (c) Atoms are conserved
- (d) All of these
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What is the color of copper sulphate solution?
- (a) Green
- (b) Blue
- (c) Red
- (d) Colorless
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When iron nails are placed in copper sulphate solution:
- (a) Blue color intensifies
- (b) A red-brown coating forms on the nail
- (c) Green precipitate forms
- (d) No reaction occurs
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Thermal decomposition of calcium carbonate gives:
- (a) CaO and CO₂
- (b) CaO and H₂O
- (c) Ca(OH)₂ and CO₂
- (d) Ca and CO₂
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Which of the following is a combination reaction?
- (a) 2Mg + O₂ → 2MgO
- (b) CaCO₃ → CaO + CO₂
- (c) Zn + CuSO₄ → ZnSO₄ + Cu
- (d) BaCl₂ + Na₂SO₄ → BaSO₄ + 2NaCl
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Which substance is oxidized in the reaction:
- (a) Zn
- (b) Cu
- (c) SO₄
- (d) None
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The equation is an example of:
- (a) Endothermic reaction
- (b) Combination and exothermic reaction
- (c) Decomposition
- (d) Photochemical reaction
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Which of the following statements is true for a redox reaction?
- (a) Only oxidation occurs
- (b) Only reduction occurs
- (c) Both oxidation and reduction occur simultaneously
- (d) No change in oxidation state
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