1. Chemical Reactions and Equations

*नोट: यह सेक्शन रिवीजन के लिए है। अपना ज्ञान परखने के लिए ऊपर दिए गए क्विज़ में भाग लें।

1. Which of the following does not change during a chemical reaction?
   A) State  |  B) Color  |  C) Total Mass  |  D) Temperature
2. Why is magnesium ribbon cleaned before burning?
   A) To increase brightness  |  B) To remove the layer of magnesium oxide  |  C) To remove moisture  |  D) None of these
3. What is the chemical formula of Quick lime?
   A) Ca(OH)2  |  B) CaCO3  |  C) CaO  |  D) CaCl2
4. Respiration is considered which type of reaction?
   A) Endothermic  |  B) Exothermic  |  C) Decomposition  |  D) Displacement
5. The reaction CaO + H2O → Ca(OH)2 is an example of:
   A) Decomposition  |  B) Combination  |  C) Displacement  |  D) Double Displacement
6. Rusting of iron is a:
   A) Physical change  |  B) Chemical change  |  C) Biological change  |  D) None of these
7. The substances written on the left side of a chemical equation are called:
   A) Products  |  B) Reactants  |  C) Catalysts  |  D) Mixtures
8. What is the color of the precipitate formed by the reaction of potassium iodide and lead nitrate?
   A) White  |  B) Yellow  |  C) Blue  |  D) Green
9. What happens to the color of lime water when CO2 is passed through it?
   A) Turns black  |  B) Turns milky  |  C) Turns red  |  D) Remains transparent
10. Who gave the Law of Conservation of Mass?
    A) Dalton  |  B) Lavoisier  |  C) Newton  |  D) Mendeleev
11. The decomposition of vegetable matter into compost is an example of:
    A) Endothermic reaction  |  B) Exothermic reaction  |  C) Displacement reaction  |  D) Combination reaction
12. Magnesium ribbon burns in air with which color flame?
    A) Red  |  B) Dazzling white  |  C) Blue  |  D) Yellow
13. What does the symbol '(aq)' represent in a chemical equation?
    A) Solid  |  B) Liquid  |  C) Aqueous solution  |  D) Gas
14. The evolution of a gas is represented by which symbol?
    A) ↓  |  B) ↑  |  C) →  |  D) ∆
15. Formation of curd from milk is a:
    A) Physical change  |  B) Chemical change  |  C) Reversible change  |  D) None of these
16. Which gas is evolved when zinc reacts with dilute sulphuric acid?
    A) Oxygen  |  B) Hydrogen  |  C) Nitrogen  |  D) Chlorine
17. Balancing of a chemical equation is based on which law?
    A) Conservation of Energy  |  B) Conservation of Mass  |  C) Constant Proportions  |  D) None of these
18. What is the chemical formula of Marble?
    A) CaO  |  B) Ca(OH)2  |  C) CaCO3  |  D) CaSO4
19. Fermentation of grapes is a:
    A) Chemical change  |  B) Physical change  |  C) Biological change  |  D) Both A and C
20. The new substances formed after a reaction are called:
    A) Reactants  |  B) Products  |  C) Mixtures  |  D) Elements
21. Fe2O3 + 2Al → Al2O3 + 2Fe is an example of which reaction?
    A) Combination  |  B) Double Displacement  |  C) Decomposition  |  D) Displacement
22. Which brown colored gas is evolved on heating lead nitrate Pb(NO3)2?
    A) O2  |  B) NO2  |  C) N2  |  D) CO2
23. What is the color of silver chloride (AgCl) when kept in sunlight?
    A) Black  |  B) Grey  |  C) Blue  |  D) Red
24. What happens to the color of copper sulphate solution when an iron nail is placed in it?
    A) Deep blue  |  B) Pale green  |  C) Colorless  |  D) Red
25. When a decomposition reaction is carried out by heating, it is called:
    A) Thermal Decomposition  |  B) Electrolytic Decomposition  |  C) Photochemical Decomposition  |  D) None of these
26. Which gas is collected at the cathode during the electrolysis of water?
    A) Oxygen  |  B) Hydrogen  |  C) Ozone  |  D) Chlorine
27. Which gas is flushed in bags of chips to prevent oxidation?
    A) Oxygen  |  B) Nitrogen  |  C) Helium  |  D) CO2
28. Silver bromide (AgBr) is used in:
    A) Painting  |  B) Black and white photography  |  C) Fertilizers  |  D) Welding
29. A reaction in which there is an exchange of ions between the reactants is:
    A) Displacement  |  B) Double Displacement  |  C) Combination  |  D) Decomposition
30. Oxidation is a process which involves:
    A) Addition of oxygen  |  B) Removal of hydrogen  |  C) Loss of electrons  |  D) All of the above
31. Reduction is a process which involves:
    A) Removal of oxygen  |  B) Addition of hydrogen  |  C) Both A and B  |  D) Addition of oxygen
32. The reaction between sodium sulphate and barium chloride forms a white precipitate of:
    A) NaCl  |  B) BaSO4  |  C) Na2S  |  D) Cl2
33. What is a Redox Reaction?
    A) Only oxidation  |  B) Only reduction  |  C) Oxidation and reduction occurring simultaneously  |  D) Combination
34. An example of an endothermic reaction is:
    A) Slaking of lime  |  B) Respiration  |  C) Decomposition of silver chloride by sunlight  |  D) Burning of natural gas
35. Why is paint applied on iron articles?
    A) For beauty  |  B) To prevent corrosion  |  C) To increase weight  |  D) For sun protection
36. What is the main cause of Rancidity?
    A) Oxidation of fats and oils  |  B) Addition of water  |  C) Keeping it cold  |  D) Addition of salt
37. A skeletal equation is:
    A) Balanced  |  B) Unbalanced  |  C) Ionic  |  D) None of these
38. The 'Hit and Trial' method is used for:
    A) Finding elements  |  B) Balancing equations  |  C) Changing colors  |  D) None of these
39. What is the formula of Slaked lime?
    A) CaO  |  B) Ca(OH)2  |  C) CaCO3  |  D) CaCl2
40. Burning of natural gas (Methane) is which type of reaction?
    A) Endothermic  |  B) Exothermic  |  C) Displacement  |  D) Double Displacement
41. In the reaction CuO + H2 → Cu + H2O, the substance oxidized is:
    A) CuO  |  B) H2  |  C) Cu  |  D) H2O
42. What color coating is formed on Copper due to corrosion?
    A) Black  |  B) Green  |  C) Brown  |  D) White
43. Why is decomposition considered opposite to combination?
    A) Energy is released  |  B) Two reactants combine  |  C) A single reactant breaks down to give simpler products  |  D) None of these
44. A shiny brown element 'X' on heating in air becomes black. 'X' is:
    A) Mg  |  B) Fe  |  C) Cu  |  D) Al
45. What is added to fat-containing food to keep it fresh?
    A) Oxidizing agents  |  B) Anti-oxidants  |  C) Water  |  D) Vinegar
46. Shiny finish on walls after 2-3 days of white washing is due to the formation of:
    A) CaO  |  B) CaCO3  |  C) Ca(OH)2  |  D) Sunlight
47. In the electrolysis of water, the volume ratio of hydrogen and oxygen is:
    A) 1:1  |  B) 2:1  |  C) 1:2  |  D) 8:1
48. Black coating on silver is an example of:
    A) Decomposition  |  B) Corrosion  |  C) Rancidity  |  D) Combination
49. In MnO2 + 4HCl → MnCl2 + 2H2O + Cl2, which is the oxidizing agent?
    A) HCl  |  B) MnO2  |  C) H2O  |  D) Cl2
50. Which change is observed during the reaction of Zinc with dilute sulphuric acid?
    A) Increase in temperature  |  B) Evolution of H2 gas  |  C) Both A and B  |  D) Change in color
51. In the reaction Fe + CuSO4 → FeSO4 + Cu, what is happening to iron?
    A) Reduction  |  B) Oxidation  |  C) Decomposition  |  D) None of these
52. What is obtained from a precipitation reaction?
    A) Soluble salt  |  B) Insoluble salt  |  C) Gas  |  D) Liquid
53. The solution used for whitewashing (Ca(OH)2) reacts with which atmospheric gas?
    A) O2  |  B) CO2  |  C) N2  |  D) H2
54. 2AgBr → 2Ag + Br2 (in sunlight) is which type of reaction?
    A) Thermal decomposition  |  B) Photochemical decomposition  |  C) Electrolytic  |  D) Combination
55. Corrosion is harmful because it destroys the ________ of metals:
    A) Color  |  B) Strength and life  |  C) Weight  |  D) Luster
56. To prevent rancidity, food items should be kept in:
    A) Sunlight  |  B) Air-tight containers  |  C) Open air  |  D) Hot places
57. Lead is ________ compared to Copper:
    A) Less reactive  |  B) More reactive  |  C) Inert  |  D) Equally reactive
58. In a chemical reaction, the arrowhead points towards the:
    A) Reactants  |  B) Products  |  C) Upwards  |  D) Downwards
59. The reaction between Barium chloride and Aluminium sulphate forms a precipitate of:
    A) AlCl3  |  B) BaSO4  |  C) BaCl2  |  D) None of these
60. Which of the following is a physical change?
    A) Cooking of food  |  B) Melting of wax  |  C) Rusting of iron  |  D) Burning of paper