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