Tiêu đề 1 Chemical reactions and equations - MCQs.pdf ✅

© www.bankofbiology.com 8921 510 476 1 1. CHEMICAL REACTIONS AND EQUATIONS: MCQs 1. Which of the following processes does not involve a chemical reaction? (a) Melting of candle (b) Burning of candle (c) Digestion of food (d) Ripening of banana Answer: (a) Melting of candle 2. Which one is an example of a chemical reaction? (a) Grapes get fermented (b) Breakdown of food (c) Formation of curd (d) All of the above Answer: (d) All of the above 3. How can the following reaction be classified? CO2 + 2H2 → CH3OH a. This is a combination reaction as a compound separates into two compounds. b. This is a decomposition reaction as a compound dissociates into two compounds. c. This is a combination reaction as two compounds react to form a single compound. d. This is a decomposition reaction as two compounds react to form a single compound. Answer: (c) 4. 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 Heat → 2PbO + 4NO2 + O2 Answer: (b) 2Na + 2H2O → 2NaOH + H2 5. A student performs an experiment to form aluminium chloride from aluminium and chlorine. Which of the following option gives the chemical equation of the reaction? a. Al + Cl2 → AlCl2 b. 2Al + Cl2 → 2AlCl c. 2Al + 3Cl2 → 2AlCl3 d. 3Al + 3Cl2 → 3AlCl3 Answer: (c) 2Al + 3Cl2 → 2AlCl3 6. Magnesium ribbon is rubbed before burning because it has a coating of a. basic magnesium carbonate b. basic magnesium sulphide c. basic magnesium chloride d. basic magnesium oxide Answer: (d) basic magnesium oxide 7. The chemical formula of magnesium oxide is ______. a. MgO2 b. Mg2O c. MgO d. Mg(OH)2 Answer: (c) MgO 8. Which of the following are exothermic processes? (i) Reaction of water with quick lime (ii) Dilution of an acid (iii) Evaporation of water (iv) Sublimation of camphor (crystals) a. (i) and (iv) b. (i) and (ii) c. (ii) and (iii) d. (ii) and (iv) Answer: (b) (i) and (ii) 9. Which of the following statements about the given reaction are correct? 3Fe (s) + 4H2O (g) → Fe3O4 (s) + 4 H2 (g) (i) Iron metal is getting oxidised (ii) Water is getting reduced (iii) Water is acting as reducing agent (iv) Water is acting as oxidising agent a. (i), (ii) and (iii) b. (iii) and (iv) c. (i), (ii) and (iv) d. (ii) and (iv) Answer: (c) (i), (ii) and (iv) 10. The addition of oxygen to a substance is called ................... and removal of oxygen is called ................... (a) Oxidation, reduction (b) Reduction, oxidation (c) Combustion, reduction (d) Reduction, combustion Answer: (a) Oxidation, reduction 11. Precipitation reactions produce insoluble: (a) Salts (b) Gases (c) Metals (d) Acids Answer: (a) Salts 12. The addition of hydrogen to a substance is called ............... and removal of hydrogen is called ............... (a) Hydrogenation, Dehydrogenation (b) Dehydrogenation, Hydrogenation (c) Reduction, oxidation (d) Oxidation, reduction Answer: (c) Reduction, oxidation 13. ............. is the process in which metals are eaten up gradually by the action of air, moisture or a chemical on their surface. (a) Combustion (b) Corrosion (c) Oxidation (d) Reduction Answer: (b) Corrosion 14. Reduction is a process of a. addition of oxygen b. gain of electrons c. loss of electrons d. removal of hydrogen Answer: (b) gain of electrons 15. Oxidation is a process which involves a. Addition of oxygen b. Loss of electrons c. Removal of hydrogen d. All of the above Answer: (d) All of the above
© www.bankofbiology.com 8921 510 476 2 16. Given below is a reaction between zinc and hydrogen. Zn + 2H+ → Zn2+ + H2 Which shows oxidation? (a) Zn → Zn+2 (b) 2H+ → H2 (c) Zn+2 → Zn (d) H2 → 2H+ Answer: (a) Zn → Zn+2 17. Three beakers labelled as A, B and C each containing 25 ml of water were taken. A small amount of NaOH, anhydrous CuSO4 and NaCl were added to the beakers A, B and C respectively. It was observed that there was an increase in the temperature of the solution contained in beakers A and B, whereas in case of beaker C, the temperature of the solution falls. Which one of the following statement(s) is (are) correct? (i) In beakers A and B, exothermic process has occurred. (ii) In beakers A and B, endothermic process has occurred. (iii) In beaker C exothermic process has occurred. (iv) In beaker C endothermic process has occurred. (a) (i) only (b) (ii) only (c) (i) and (iv) (d) (iv), (ii) and (iii) Answer: (c) (i) and (iv) 18. Which among the following statement(s) is (are) true? Exposure of silver chloride to sunlight for a long duration turns grey due to (i) formation of silver by decomposition of silver chloride (ii) sublimation of silver chloride (iii) decomposition of chlorine gas from silver chloride (iv) oxidation of silver chloride (a) (i) only (b) (i) and (iii) (c) (ii) and (iii) (d) (iv) only Answer: (a) (i) only 19. Which of the following reactions is used in black-and- white photography? (a) Combination reaction (b) Decomposition reaction (c) Displacement reaction (d) Oxidation reaction Answer: (b) Decomposition reaction 20. MnO2 + 4HCl → MnCl2 + 2H2O + Cl2 Identify the substance oxidized in the above equation. (a) MnCl2 (b) HCl (c) H2O (d) MnO2 Answer: (b) HCl 21. The chemical reaction between potassium chloride and silver nitrate is given below: AgNO3 + KCl → AgCl + KNO3 What can be inferred from the chemical equation? a. Silver nitrate & potassium undergo decomposition reaction to form silver chloride & potassium nitrate b. Silver nitrate & potassium undergo a displacement reaction to form silver chloride & potassium nitrate c. Silver nitrate & potassium undergo a combination reaction to form silver chloride & potassium nitrate d. Silver nitrate & potassium undergo a double displacement reaction to form silver chloride & potassium nitrate Answer: (d) 22. A student adds lead and silver to two different test tubes containing an equal amount of copper sulphate solution. The student observes that the colour of the solution in the test tube with lead changes. What explains the change in the colour of the solution? a. A displacement reaction takes place as lead replaces copper from the solution. b. A combination reaction takes place as lead combines with sulphate in the solution. c. A decomposition reaction takes place as copper dissociates from sulphate in the solution. d. A double displacement reaction takes place as copper dissociates from sulphate and lead combines with sulphate in the solution. Answer: (a) 23. Give the ratio in which hydrogen and oxygen are present in water by volume. (a) 1:2 (b) 1:1 (c) 2:1 (d) 1:8 Answer: (c) 2:1 24. A substance ‘X’ is used in white-washing and is obtained by heating limestone in the absence of air. Identify ‘X’. (a) CaOCl2 (b) Ca (OH)2 (c) CaO (d) CaCO3 Answer: (c) CaO 25. When Ag is exposed to air it gets a black coating of (a) AgNO3 (b) Ag2S (c) Ag2O (d) Ag2CO3 Answer: (b) Ag2S 26. Na2SO4 + BaCl2 → ............. + 2NaCl (a) BaSO4 (b) NaCl (c) Na2Cl (d) Ba2SO4 Answer: (a) BaSO4 27. 2 FeSO4 → Fe2O3 + SO2 + ............. (a) SO3 (b) H2 (c) H2O (d) CO2 Answer: (a) SO3 28. Which of the following is an endothermic process? (a) Dilution of sulphuric acid (b) Sublimation of dry ice (c) Condensation of water vapours (d) Respiration in human beings
© www.bankofbiology.com 8921 510 476 3 Answer: (b) Sublimation of dry ice 29. Barium hydroxide is added to hydrochloric acid to form a white-coloured barium chloride. Which of the following gives the balanced chemical equation? (a) HCl + Ba(OH)2 → BaCl2 + 2HOH (b) 2HCl + Ba(OH)2 → BaCl2 + 2HOH (c) 2HCl + Ba(OH)2 → BaH2 + 2HCl + O2 (d) HCl + 2Ba(OH) → 2BaCl2 + 2HOH + O2 Answer: (b) 2HCl + Ba(OH)2 → BaCl2 + 2HOH 30. What type of chemical reactions take place when electricity is passed through water? (a) Displacement (b) Combination (c) Decomposition (d) Double displacement Answer: (c) Decomposition 31. 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 (b) Lead acetate (c) Ammonium nitrate (d) Potassium sulphate Answer: (b) Lead acetate 32. Select the oxidising agent for the following reaction: H2S + I2 → 2HI + S (a) I2 (b) H2S (C) HI (d) S Answer: (a) I2 33. The condition due to aerial oxidation of fats and oils in foods marked by unpleasant smell and taste is called (a) antioxidation (b) reduction (c) rancidity (d) corrosion Answer: (c) rancidity 34. A substance added to food containing fats and oils is (a) Oxidant (b) Rancid (c) Coolant (d) Antioxidant Answer: (d) Antioxidant 35. Electrolysis of water is a decomposition reaction. The mole ratio of hydrogen and oxygen gases liberated during electrolysis of water is: (a) 1:1 (b) 2:1 (c) 4:1 (d) 1:2 Answer: (b) 2:1 36. When SO2 gas is passed through saturated solution of H2S, which of the following reaction occurs? (a) SO2 + 2H2S → 2H2O + 3S (b) SO2 + 2H2S → H2O + 3S (c) SO2 + H2S → H2O + S (d) SO2 + H2O → SO3 + H2 Answer: (a) SO2 + 2H2S → 2H2O + 3S 37. Reactions in which energy is given out are known as: (a) Exothermic (b) Endothermic (c) Combustion (d) Decomposition Answer: (a) Exothermic 38. Name the products formed when iron filings are heated with dilute hydrochloric acid. (a) Fe (III) chloride and water (b) Fe (II) chloride and water (c) Fe (II) chloride and hydrogen gas (d) Fe (III) chloride and hydrogen gas Answer: (c) Fe (II) chloride and hydrogen gas 39. Pb + CuCl2 → PbCl2 + Cu The above reaction is an example of: (a) combination (b) double displacement (c) decomposition (d) displacement Answer: (d) displacement 40. Reaction in which an element displaces another element from its compound is called (a) Substitution (b) Combustion (c) Displacement (d) Decomposition Answer: (c) Displacement 41. A dilute ferrous sulphate solution was gradually added to the beaker containing acidified permanganate solution. The light purple colour of the solution fades and finally disappears. Which is the correct explanation for the observation? (a) KMnO4 is an oxidising agent, it oxidises FeSO4. (b) FeSO4 acts as an oxidising agent and oxidises KMNO4. (c) The colour disappears due to dilution; no reaction is involved. (d) KMnO4 is an unstable compound and decomposes in presence of FeSO4. to a colourless compound. Answer: (a) KMnO4 is an oxidising agent, it oxidises FeSO4 42. Which of the following gases can be used for storage? (a) CO2 or Oxygen (b) Nitrogen or Oxygen (c) CO2 or Helium (d) Helium or Nitrogen Answer: (d) Helium or Nitrogen 43. Chemical equations, the abbreviations represent the correct states of the reactants and products involved at reaction temperature? (a) 2H2 (l) + O2 (l) → 2H2O(g) (b) 2H2 (g) + O2 (l) → 2H2O (l) (c) 2H2 (g) + O2 (g) → 2H2O (l) (d) 2H2 (g) +O2 (g) → 2H2O (g) Answer: (d) 2H2 (g) +O2 (g) → 2H2O (g)