100 MCQs Chemical Reactions and Equations. Class X Science.

Class 10 Science – Chapter 1 MCQs with Answers

Chapter: Chemical Reactions and Equations

1. What is a chemical reaction?

A) Change in size
B) Change in state only
C) Process in which new substances are formed
D) Melting of ice

Answer: C) Process in which new substances are formed


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2. Which of the following indicates a chemical reaction?

A) Change in colour
B) Evolution of gas
C) Formation of precipitate
D) All of these

Answer: D) All of these


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3. Magnesium ribbon burns in air with:

A) Yellow flame
B) Blue flame
C) Dazzling white flame
D) Red flame

Answer: C) Dazzling white flame


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4. What is formed when magnesium burns in oxygen?

A) Magnesium chloride
B) Magnesium oxide
C) Magnesium sulphate
D) Magnesium nitrate

Answer: B) Magnesium oxide


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5. A balanced chemical equation obeys:

A) Law of gravity
B) Law of conservation of mass
C) Newton’s law
D) Ohm’s law

Answer: B) Law of conservation of mass


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6. Which symbol represents gas in a chemical equation?

A) (l)
B) (s)
C) (g)
D) (aq)

Answer: C) (g)


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7. Which reaction releases heat?

A) Endothermic reaction
B) Exothermic reaction
C) Displacement reaction
D) Double displacement reaction

Answer: B) Exothermic reaction


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8. Respiration is an example of:

A) Endothermic reaction
B) Exothermic reaction
C) Photochemical reaction
D) Neutralization reaction

Answer: B) Exothermic reaction


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9. The reaction in which a substance gains oxygen is called:

A) Reduction
B) Oxidation
C) Neutralization
D) Combination

Answer: B) Oxidation


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10. Rusting of iron is an example of:

A) Reduction
B) Corrosion
C) Crystallization
D) Sublimation

Answer: B) Corrosion


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11. Which gas is evolved when zinc reacts with dilute acid?

A) Oxygen
B) Nitrogen
C) Hydrogen
D) Carbon dioxide

Answer: C) Hydrogen


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12. Combination reaction means:

A) One substance breaks down
B) Two or more substances combine to form one product
C) Exchange of ions
D) Removal of oxygen

Answer: B) Two or more substances combine to form one product


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13. What type of reaction is:

CaO + H₂O → Ca(OH)₂

A) Decomposition reaction
B) Combination reaction
C) Displacement reaction
D) Redox reaction

Answer: B) Combination reaction


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14. Decomposition reactions require:

A) Heat, light, or electricity
B) Water only
C) Oxygen only
D) Pressure only

Answer: A) Heat, light, or electricity


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15. Electrolysis of water is a:

A) Combination reaction
B) Decomposition reaction
C) Neutralization reaction
D) Corrosion reaction

Answer: B) Decomposition reaction


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16. The reaction in which more reactive element displaces a less reactive element is called:

A) Double displacement reaction
B) Combination reaction
C) Displacement reaction
D) Thermal decomposition

Answer: C) Displacement reaction


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17. What happens when iron nail is dipped in copper sulphate solution?

A) No reaction
B) Solution becomes colourless
C) Iron displaces copper
D) Copper displaces iron

Answer: C) Iron displaces copper


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18. Double displacement reactions usually form:

A) Gas only
B) Water only
C) Precipitate
D) Oxygen

Answer: C) Precipitate


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19. White silver chloride turns grey in sunlight due to:

A) Oxidation
B) Reduction
C) Photochemical decomposition
D) Neutralization

Answer: C) Photochemical decomposition


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20. What is rancidity?

A) Rusting of iron
B) Spoilage of food due to oxidation
C) Formation of salts
D) Evaporation of liquids

Answer: B) Spoilage of food due to oxidation


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21. Which substance is used to prevent rancidity in food packets?

A) Oxygen
B) Nitrogen
C) Hydrogen
D) Carbon dioxide

Answer: B) Nitrogen


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22. Which reaction absorbs heat?

A) Exothermic reaction
B) Endothermic reaction
C) Combination reaction
D) Corrosion reaction

Answer: B) Endothermic reaction


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23. Digestion of food is an example of:

A) Endothermic reaction
B) Exothermic reaction
C) Photolysis
D) Neutralization

Answer: B) Exothermic reaction


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24. Which of the following is a chemical change?

A) Melting wax
B) Boiling water
C) Burning paper
D) Freezing milk

Answer: C) Burning paper


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25. What is the colour of copper sulphate solution?

A) Green
B) Blue
C) Red
D) Yellow

Answer: B) Blue


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26. The reaction:

2AgCl → 2Ag + Cl₂
is an example of: A) Combination reaction
B) Thermal decomposition
C) Photochemical decomposition
D) Displacement reaction

Answer: C) Photochemical decomposition


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27. Oxidation and reduction occur:

A) Separately
B) Together
C) Never together
D) Only in acids

Answer: B) Together


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28. Which metal does not rust?

A) Iron
B) Copper
C) Aluminium
D) Gold

Answer: D) Gold


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29. Which of the following is a balanced equation?

A) H₂ + O₂ → H₂O
B) 2H₂ + O₂ → 2H₂O
C) H₂ + O₂ → H₂O₂
D) H₂O → H₂ + O₂

Answer: B) 2H₂ + O₂ → 2H₂O


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30. Corrosion of silver is called:

A) Rusting
B) Tarnishing
C) Rancidity
D) Crystallization

Answer: B) Tarnishing


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31. What is the formula of quick lime?

A) CaCO₃
B) Ca(OH)₂
C) CaO
D) CaCl₂

Answer: C) CaO


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32. Which reaction produces electricity?

A) Redox reaction
B) Combination reaction
C) Thermal decomposition
D) Neutralization

Answer: A) Redox reaction


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33. Green coating on copper is due to:

A) Copper oxide
B) Basic copper carbonate
C) Copper sulphate
D) Copper chloride

Answer: B) Basic copper carbonate


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34. Which process is involved in rusting?

A) Reduction
B) Oxidation
C) Sublimation
D) Neutralization

Answer: B) Oxidation


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35. A precipitate is:

A) A gas formed
B) Insoluble solid formed in solution
C) Liquid formed
D) Metal formed

Answer: B) Insoluble solid formed in solution


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36. Which is a decomposition reaction?

A) CaO + H₂O → Ca(OH)₂
B) Zn + CuSO₄ → ZnSO₄ + Cu
C) 2KClO₃ → 2KCl + 3O₂
D) Fe + S → FeS

Answer: C) 2KClO₃ → 2KCl + 3O₂


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37. Which gas supports combustion?

A) Nitrogen
B) Oxygen
C) Hydrogen
D) Carbon dioxide

Answer: B) Oxygen


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38. Which reaction is used in photography?

A) Thermal decomposition
B) Photochemical decomposition
C) Neutralization
D) Respiration

Answer: B) Photochemical decomposition


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39. Which of these is a physical change?

A) Rusting
B) Burning
C) Melting ice
D) Digestion

Answer: C) Melting ice


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40. What is the colour of iron sulphate crystals?

A) Blue
B) Green
C) White
D) Yellow

Answer: B) Green


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Class 10 Science – Chapter 1 MCQs with Answers

Questions 41–100

Chapter: Chemical Reactions and Equations


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41. Which metal is used in thermite reaction?

A) Copper
B) Iron
C) Aluminium
D) Zinc

Answer: C) Aluminium


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42. Thermite reaction is an example of:

A) Endothermic reaction
B) Exothermic reaction
C) Neutralization reaction
D) Decomposition reaction

Answer: B) Exothermic reaction


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43. Which substance is oxidized in the reaction:

CuO + H₂ → Cu + H₂O

A) Copper oxide
B) Hydrogen
C) Copper
D) Water

Answer: B) Hydrogen


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44. Which substance is reduced in the above reaction?

A) Hydrogen
B) Water
C) Copper oxide
D) Oxygen

Answer: C) Copper oxide


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45. Which process causes blackening of silver?

A) Rancidity
B) Corrosion
C) Combustion
D) Crystallization

Answer: B) Corrosion


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46. Which of the following is not a chemical reaction?

A) Burning coal
B) Rusting iron
C) Melting butter
D) Digestion of food

Answer: C) Melting butter


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47. Which type of reaction is represented by:

Fe + CuSO₄ → FeSO₄ + Cu

A) Combination reaction
B) Double displacement reaction
C) Displacement reaction
D) Decomposition reaction

Answer: C) Displacement reaction


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48. The chemical formula of rust is:

A) Fe₂O₃
B) Fe₂O₃·xH₂O
C) FeSO₄
D) Fe₃O₄

Answer: B) Fe₂O₃·xH₂O


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49. Which reaction occurs when food is digested?

A) Oxidation
B) Reduction
C) Neutralization
D) Photolysis

Answer: A) Oxidation


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50. What is formed when lead nitrate is heated?

A) Lead oxide, nitrogen dioxide, and oxygen
B) Lead chloride only
C) Nitrogen only
D) Lead sulphate

Answer: A) Lead oxide, nitrogen dioxide, and oxygen


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51. Which gas has a brown colour during decomposition of lead nitrate?

A) Oxygen
B) Nitrogen
C) Nitrogen dioxide
D) Hydrogen

Answer: C) Nitrogen dioxide


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52. What is the nature of decomposition reactions?

A) Require energy
B) Release energy
C) No energy change
D) Only light energy

Answer: A) Require energy


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53. Which reaction is also called precipitation reaction?

A) Combination reaction
B) Double displacement reaction
C) Oxidation reaction
D) Reduction reaction

Answer: B) Double displacement reaction


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54. Which of the following is a redox reaction?

A) HCl + NaOH → NaCl + H₂O
B) CuO + H₂ → Cu + H₂O
C) CaO + H₂O → Ca(OH)₂
D) AgNO₃ + NaCl → AgCl + NaNO₃

Answer: B) CuO + H₂ → Cu + H₂O


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55. The substance that loses oxygen is said to be:

A) Oxidized
B) Reduced
C) Neutralized
D) Hydrolyzed

Answer: B) Reduced


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56. Which chemical is formed when iron reacts with oxygen and moisture?

A) Iron sulphide
B) Rust
C) Iron nitrate
D) Copper oxide

Answer: B) Rust


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57. Which of the following prevents rusting?

A) Painting
B) Galvanization
C) Oiling
D) All of these

Answer: D) All of these


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58. Galvanization is the process of coating iron with:

A) Copper
B) Zinc
C) Silver
D) Aluminium

Answer: B) Zinc


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59. Which metal is more reactive than copper?

A) Silver
B) Gold
C) Iron
D) Platinum

Answer: C) Iron


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60. Which reaction takes place during respiration?

A) Endothermic
B) Exothermic
C) Displacement
D) Double displacement

Answer: B) Exothermic


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61. Which catalyst is used in decomposition of hydrogen peroxide?

A) Sodium chloride
B) Manganese dioxide
C) Copper sulphate
D) Zinc oxide

Answer: B) Manganese dioxide


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62. What is the colour of silver chloride precipitate?

A) Blue
B) Green
C) White
D) Brown

Answer: C) White


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63. Which reaction forms a single product?

A) Combination reaction
B) Decomposition reaction
C) Displacement reaction
D) Double displacement reaction

Answer: A) Combination reaction


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64. The reaction:

2H₂ + O₂ → 2H₂O
is: A) Decomposition reaction
B) Combination reaction
C) Displacement reaction
D) Reduction reaction

Answer: B) Combination reaction


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65. Which of the following is a chemical property?

A) Colour
B) Melting point
C) Reactivity
D) Density

Answer: C) Reactivity


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66. Which reaction is involved in the manufacture of curd from milk?

A) Physical change
B) Chemical change
C) Sublimation
D) Freezing

Answer: B) Chemical change


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67. What is produced when carbon burns in oxygen?

A) Carbon monoxide
B) Carbon dioxide
C) Sulphur dioxide
D) Nitrogen dioxide

Answer: B) Carbon dioxide


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68. Which type of reaction is photosynthesis?

A) Endothermic reaction
B) Exothermic reaction
C) Displacement reaction
D) Neutralization reaction

Answer: A) Endothermic reaction


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69. Which gas is usually filled in chips packets?

A) Oxygen
B) Hydrogen
C) Nitrogen
D) Helium

Answer: C) Nitrogen


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70. Which of the following is not an indicator of chemical reaction?

A) Change in temperature
B) Change in colour
C) Formation of gas
D) Change in shape only

Answer: D) Change in shape only


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71. Which reaction releases oxygen gas?

A) Decomposition of KClO₃
B) Rusting
C) Neutralization
D) Respiration

Answer: A) Decomposition of KClO₃


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72. The reaction in which heat is evolved is called:

A) Endothermic reaction
B) Exothermic reaction
C) Reduction reaction
D) Oxidation reaction

Answer: B) Exothermic reaction


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73. Which substance is added to prevent oxidation in foods?

A) Antioxidants
B) Acids
C) Bases
D) Salts

Answer: A) Antioxidants


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74. Which metal is least reactive?

A) Sodium
B) Potassium
C) Gold
D) Calcium

Answer: C) Gold


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75. What is the colour of copper metal deposited in CuSO₄ reaction?

A) Blue
B) Red-brown
C) Black
D) White

Answer: B) Red-brown


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76. Which process is responsible for digestion?

A) Physical change
B) Chemical change
C) Sublimation
D) Freezing

Answer: B) Chemical change


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77. Which reaction is used for welding railway tracks?

A) Combination reaction
B) Thermite reaction
C) Neutralization reaction
D) Photolysis

Answer: B) Thermite reaction


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78. What type of reaction is:

AgNO₃ + NaCl → AgCl + NaNO₃

A) Combination reaction
B) Double displacement reaction
C) Displacement reaction
D) Decomposition reaction

Answer: B) Double displacement reaction


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79. What happens during oxidation?

A) Gain of electrons
B) Loss of oxygen
C) Gain of oxygen
D) Gain of hydrogen

Answer: C) Gain of oxygen


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80. Which reaction absorbs sunlight energy?

A) Respiration
B) Combustion
C) Photosynthesis
D) Rusting

Answer: C) Photosynthesis


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81. Which metal reacts vigorously with water?

A) Sodium
B) Gold
C) Silver
D) Copper

Answer: A) Sodium


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82. What is the purpose of balancing chemical equations?

A) To increase products
B) To follow law of conservation of mass
C) To reduce reactants
D) To change formula

Answer: B) To follow law of conservation of mass


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83. Which gas is produced during respiration?

A) Oxygen
B) Carbon dioxide
C) Hydrogen
D) Nitrogen

Answer: B) Carbon dioxide


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84. Which reaction is represented by:

2Pb(NO₃)₂ → 2PbO + 4NO₂ + O₂

A) Combination reaction
B) Decomposition reaction
C) Displacement reaction
D) Neutralization reaction

Answer: B) Decomposition reaction


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85. Which process causes bad smell in oily foods?

A) Corrosion
B) Rancidity
C) Reduction
D) Sublimation

Answer: B) Rancidity


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86. Which metal is protected by galvanization?

A) Copper
B) Iron
C) Silver
D) Gold

Answer: B) Iron


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87. Which reaction occurs when acid reacts with base?

A) Neutralization reaction
B) Oxidation reaction
C) Displacement reaction
D) Decomposition reaction

Answer: A) Neutralization reaction


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88. Which type of reaction occurs in batteries?

A) Redox reaction
B) Neutralization
C) Combination
D) Thermal decomposition

Answer: A) Redox reaction


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89. Which compound turns black on exposure to air?

A) Silver
B) Copper
C) Iron
D) Aluminium

Answer: A) Silver


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90. The process of gaining hydrogen is called:

A) Oxidation
B) Reduction
C) Corrosion
D) Rancidity

Answer: B) Reduction


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91. Which of the following is an exothermic process?

A) Melting ice
B) Photosynthesis
C) Burning LPG
D) Boiling water

Answer: C) Burning LPG


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92. Which reaction involves exchange of ions?

A) Combination reaction
B) Double displacement reaction
C) Decomposition reaction
D) Redox reaction

Answer: B) Double displacement reaction


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93. Which metal forms green carbonate layer in air?

A) Iron
B) Copper
C) Silver
D) Zinc

Answer: B) Copper


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94. Which process needs oxygen and moisture?

A) Rusting
B) Boiling
C) Freezing
D) Melting

Answer: A) Rusting


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95. Which of the following is an endothermic reaction?

A) Respiration
B) Burning coal
C) Photosynthesis
D) Neutralization

Answer: C) Photosynthesis


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96. Which reaction produces white precipitate?

A) AgNO₃ + NaCl
B) Mg + O₂
C) Zn + HCl
D) Fe + CuSO₄

Answer: A) AgNO₃ + NaCl


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97. What is the formula of water?

A) HO
B) H₂O
C) H₂O₂
D) OH₂

Answer: B) H₂O


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98. Which reaction gives heat and light?

A) Combustion
B) Neutralization
C) Sublimation
D) Freezing

Answer: A) Combustion


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99. Which scientist proposed the law of conservation of mass?

A) Newton
B) Dalton
C) Lavoisier
D) Rutherford

Answer: C) Lavoisier


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100. Chemical equations are written using:

A) Symbols and formulae
B) Sentences only
C) Diagrams only
D) Numbers only

Answer: A) Symbols and formulae