100 Questions in O’level Chemistry for you add to your revision.

1. What is the chemical symbol for oxygen?
2. Define an element in chemistry.
3. How many valence electrons does carbon have?
4. Name two allotropes of carbon.
5. What is the formula of sulfuric acid?
6. Define an acid in chemistry.
7. What is the pH range of acidic solutions?
8. What are the products of the reaction between hydrochloric acid (HCl) and sodium hydroxide (NaOH)?
9. What is the name of the process by which solid changes directly to a gas without becoming a liquid first?
10. What are the products of the complete combustion of a hydrocarbon in excess oxygen?
11. Define the term “exothermic reaction.”
12. What type of bond forms between two nonmetals?
13. What is the balanced chemical equation for the reaction between magnesium (Mg) and oxygen (O2)?
14. Name the gas produced when acids react with metals.
15. Define a precipitate in a chemical reaction.
16. What is the formula of ammonium sulfate?
17. How many electrons can the first energy level (n=1) hold?
18. What is the formula of potassium nitrate?
19. Define a catalyst in a chemical reaction.
20. What is the molecular formula of ethanol?
21. Name two gases that cause acid rain.
22. Define an exothermic reaction.
23. What is the formula of calcium carbonate?
24. How many atoms are present in one molecule of water (H2O)?
25. Define the term “endothermic reaction.”
26. Name the process by which a solid changes directly to a gas without becoming a liquid first.
27. What is the molecular formula of glucose?
28. Define the term “reduction” in chemistry.
29. What is the chemical symbol for sodium?
30. What is the formula of nitric acid?
31. Define a base in chemistry.
32. Name the gas produced when acids react with carbonates.
33. What is the balanced chemical equation for the reaction between hydrochloric acid (HCl) and calcium carbonate (CaCO3)?
34. Define the term “activation energy.”
35. What is the molecular formula of methane?
36. What is the formula of sodium chloride?
37. Define an endothermic reaction.
38. Name the process by which a gas changes directly to a solid without becoming a liquid first.
39. What is the formula of sulfur dioxide?
40. Define the term “oxidation” in chemistry.
41. What is the chemical symbol for iron?
42. Name the type of bond that forms between a metal and a nonmetal.
43. What is the balanced chemical equation for the reaction between sulfuric acid (H2SO4) and potassium hydroxide (KOH)?
44. Define the term “valency” in chemistry.
45. What is the molecular formula of ethane?
46. What is the formula of hydrochloric acid?
47. Define the term “neutralization reaction.”
48. Name the gas produced when acids react with metal carbonates.
49. What is the chemical symbol for copper?
50. What is the formula of sodium hydroxide?
51. Define the term “molecular formula” in chemistry.
52. What is the molecular formula of propane?
53. What is the formula of nitrous acid?
54. Define the term “homologous series” in organic chemistry.
55. What is the chemical symbol for silver?
56. Name the gas produced when acids react with metal sulfites.
57. What is the formula of hydrofluoric acid?
58. Define the term “electrolysis” in chemistry.
59. What is the molecular formula of butane?
60. What is the formula of sulfur hexafluoride?
61. Define the term “atomic number” in chemistry.
62. What is the formula of acetic acid?
63. Name the gas produced when acids react with metal sulfides.
64. What is the chemical symbol for gold?
65. What is the molecular formula of pentane?
66. Define the term “isotope” in chemistry.
67. What is the formula of hydrobromic acid?
68. Name the gas produced when acids react with metal sulfates.
69. What is the chemical symbol for zinc?
70. What is the molecular formula of hexane?
71. Define the term “mole” in chemistry.
72. What is the formula of hydroiodic acid?
73. Name the gas produced when acids react with metal oxides.
74. What is the chemical symbol for chlorine?
75. What is the molecular formula of heptane?
76. Define the term “stoichiometry” in chemistry.
77. What is the formula of hydrosulfuric acid?
78. Name the gas produced when acids react with metal hydroxides.
79. What is the chemical symbol for nitrogen?
80. What is the molecular formula of octane?
81. Define the term “molar mass” in chemistry.
82. What is the formula of phosphoric acid?
83. Name the gas produced when acids react with metal hydrides.
84. What is the chemical symbol for carbon?
85. What is the molecular formula of ethene?
86. Define the term “stoichiometric ratio” in chemistry.
87. What is the formula of carbonic acid?
88. Name the gas produced when acids react with metal bicarbonates.
89. What is the chemical symbol for oxygen?
90. What is the molecular formula of propene?
91. Define the term “Avogadro’s number” in chemistry.
92. What is the formula of perchloric acid?
93. Name the gas produced when acids react with metal bicarbonates.
94. What is the chemical symbol for hydrogen?
95. What is the molecular formula of butene?
96. Define the term “empirical formula” in chemistry.
97. What is the formula of nitrous acid?
98. Name the gas produced when acids react with metal bicarbonates.
99. What is the chemical symbol for helium?
100. What is the molecular formula of pentene?

Please note that these questions cover a wide range of topics in O level Chemistry and can be used for practice and review.