1. A compound is a substance formed by:
A) Physical mixing of elements
B) Chemical combination of two or more elements
C) Mixing of atoms only
D) Separation of elements
Answer: B
2. The smallest unit of a compound that retains its properties is called:
A) Atom
B) Ion
C) Molecule
D) Electron
Answer: C
3. Water (H₂O) is a compound because:
A) It can be separated physically
B) It has fixed composition
C) It is a mixture
D) It contains only hydrogen
Answer: B
4. Which of the following is a compound?
A) Air
B) Brass
C) Sodium chloride
D) Oxygen
Answer: C
5. The chemical formula of carbon dioxide is:
A) CO
B) CO₂
C) C₂O
D) C₂O₂
Answer: B
6. A compound always contains elements in:
A) Variable ratio
B) Equal mass
C) Fixed ratio
D) Random proportion
Answer: C
7. Which compound is an acid?
A) NaCl
B) HCl
C) KOH
D) CaO
Answer: B
8. Which of the following is a base?
A) H₂SO₄
B) NaOH
C) CO₂
D) HNO₃
Answer: B
9. Table salt is chemically known as:
A) Sodium carbonate
B) Sodium chloride
C) Calcium chloride
D) Potassium nitrate
Answer: B
10. Which compound is used in baking powder?
A) Sodium bicarbonate
B) Sodium chloride
C) Potassium hydroxide
D) Magnesium oxide
Answer: A
11. The valency of oxygen in most compounds is:
A) 1
B) 2
C) 3
D) 4
Answer: B
12. Ammonia has the chemical formula:
A) NH₂
B) NH₃
C) N₂H
D) N₃H₂
Answer: B
13. Which of the following is an organic compound?
A) CO₂
B) NaCl
C) CH₄
D) H₂O
Answer: C
14. Compounds can be decomposed by:
A) Filtration
B) Evaporation
C) Chemical reaction
D) Sieving
Answer: C
15. Calcium carbonate has the formula:
A) CaCO₂
B) CaCO₃
C) Ca₂CO₃
D) Ca(CO₄)
Answer: B
16. The bond formed by sharing electrons is called:
A) Ionic bond
B) Metallic bond
C) Covalent bond
D) Hydrogen bond
Answer: C
17. Sodium chloride is formed by which type of bond?
A) Covalent bond
B) Ionic bond
C) Metallic bond
D) Hydrogen bond
Answer: B
18. Which compound is also known as slaked lime?
A) CaO
B) CaCO₃
C) Ca(OH)₂
D) CaCl₂
Answer: C
19. The formula of sulfuric acid is:
A) H₂SO₃
B) H₂SO₄
C) HSO₄
D) SO₄H₂
Answer: B
20. Which compound contains only carbon and hydrogen?
A) Alcohol
B) Hydrocarbon
C) Carbohydrate
D) Carbonate
Answer: B
21. The chemical name of rust is:
A) Iron sulfide
B) Iron carbonate
C) Hydrated iron oxide
D) Iron chloride
Answer: C
22. Which compound is commonly used as a fertilizer?
A) NH₄NO₃
B) NaCl
C) CO₂
D) H₂O
Answer: A
23. A compound formed from metal and non-metal is usually:
A) Covalent
B) Ionic
C) Organic
D) Neutral gas
Answer: B
24. The formula of methane is:
A) CH₃
B) CH₂
C) CH₄
D) C₂H₄
Answer: C
25. Which of the following is a neutral compound?
A) HCl
B) NaOH
C) NaCl
D) HNO₃
Answer: C
26. The combining capacity of an element in a compound is called:
A) Atomic number
B) Valency
C) Mass number
D) Density
Answer: B
27. Which compound is used in fire extinguishers?
A) CO₂
B) O₂
C) N₂
D) H₂
Answer: A
28. Hydrogen peroxide has the formula:
A) H₂O
B) HO₂
C) H₂O₂
D) H₃O₂
Answer: C
29. Which of the following is NOT a compound?
A) Water
B) Air
C) Ammonia
D) Carbon dioxide
Answer: B
30. The law stating compounds have fixed composition is:
A) Law of conservation of mass
B) Law of definite proportions
C) Law of multiple proportions
D) Boyle’s law
Answer: B