Chemistry JAMB Past Questions and Answers – Most Repeated

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Chemistry Jamb Past Questions and their answers.

Section 1: Chemistry JAMB Past Questions 1–20

Most repeated Chemistry JAMB Past Questions and Answers:

1. The atomic number of an element represents:
a) Number of neutrons
b) Number of protons
c) Number of electrons + neutrons
d) Number of isotopes
Answer: b) Number of protons

2. The molecular formula of water is:
a) H₂O₂
b) H₂O
c) HO₂
d) H₂O₃
Answer: b) H₂O

3. The pH of a neutral solution at 25°C is:
a) 0
b) 7
c) 14
d) 1
Answer: b) 7

4. Which of the following is an alkali metal?
a) Sodium
b) Calcium
c) Magnesium
d) Aluminum
Answer: a) Sodium

5. The gas evolved when an acid reacts with a metal is:
a) Oxygen
b) Hydrogen
c) Nitrogen
d) Carbon dioxide
Answer: b) Hydrogen

6. Avogadro’s number is approximately:
a) 6.02 × 10²³
b) 6.02 × 10²²
c) 3.0 × 10⁸
d) 1 × 10³
Answer: a) 6.02 × 10²³

7. The molar mass of CO₂ is:
a) 44 g/mol
b) 28 g/mol
c) 32 g/mol
d) 12 g/mol
Answer: a) 44 g/mol

8. Which element is a halogen?
a) Sodium
b) Chlorine
c) Oxygen
d) Calcium
Answer: b) Chlorine

9. The formula of aluminum sulfate is:
a) Al₂(SO₄)₃
b) AlSO₄
c) Al₂SO₄
d) Al(SO₄)₃
Answer: a) Al₂(SO₄)₃

10. Which of these is a noble gas?
a) Neon
b) Oxygen
c) Hydrogen
d) Nitrogen
Answer: a) Neon

11. Electrolysis of water produces:
a) Hydrogen only
b) Oxygen only
c) Hydrogen and Oxygen
d) Carbon dioxide
Answer: c) Hydrogen and Oxygen

12. The electron configuration of oxygen (atomic number 8) is:
a) 1s² 2s² 2p⁴
b) 1s² 2s² 2p⁶
c) 1s² 2p⁶
d) 1s² 2s²
Answer: a) 1s² 2s² 2p⁴

13. The common oxidation state of sodium is:
a) +1
b) -1
c) +2
d) 0
Answer: a) +1

14. Which of the following is an exothermic reaction?
a) Combustion of methane
b) Evaporation of water
c) Melting of ice
d) Boiling of water
Answer: a) Combustion of methane

15. The major constituent of natural gas is:
a) Methane
b) Ethane
c) Propane
d) Butane
Answer: a) Methane

16. The type of bond in NaCl is:
a) Covalent
b) Ionic
c) Metallic
d) Hydrogen
Answer: b) Ionic

17. The catalyst in the contact process for producing sulfuric acid is:
a) Platinum
b) Vanadium(V) oxide
c) Iron
d) Manganese dioxide
Answer: b) Vanadium(V) oxide

18. Which gas is responsible for global warming?
a) Nitrogen
b) Carbon dioxide
c) Oxygen
d) Hydrogen
Answer: b) Carbon dioxide

19. The unit of concentration is:
a) Moles per liter
b) Gram
c) Joule
d) Pascal
Answer: a) Moles per liter

20. The substance that cannot be broken down into simpler substances by chemical means is called:
a) Compound
b) Mixture
c) Element
d) Solution
Answer: c) Element

Section 2: Chemistry JAMB Past Questions 21–40

Most repeated Chemistry JAMB Past Questions and Answers:

21. Which of the following is an acid?
a) NaOH
b) HCl
c) KCl
d) NH₃
Answer: b) HCl

22. The formula of gypsum is:
a) CaSO₄·2H₂O
b) CaCO₃
c) CaSO₄
d) CaCl₂
Answer: a) CaSO₄·2H₂O

23. Which element is in period 2 and group 16 of the periodic table?
a) Oxygen
b) Sulfur
c) Nitrogen
d) Fluorine
Answer: a) Oxygen

24. The process of converting a solid directly to gas is called:
a) Condensation
b) Sublimation
c) Vaporization
d) Melting
Answer: b) Sublimation

25. The simplest form of matter is:
a) Atom
b) Molecule
c) Compound
d) Mixture
Answer: a) Atom

26. The reaction 2H₂ + O₂ → 2H₂O is an example of:
a) Decomposition
b) Combination
c) Displacement
d) Redox
Answer: b) Combination

27. The valency of carbon in methane is:
a) 2
b) 4
c) 1
d) 3
Answer: b) 4

28. Which of these is a polar molecule?
a) CO₂
b) H₂O
c) CH₄
d) O₂
Answer: b) H₂O

29. The process of separating liquids with different boiling points is called:
a) Filtration
b) Distillation
c) Evaporation
d) Sublimation
Answer: b) Distillation

30. The formula of baking soda is:
a) NaHCO₃
b) Na₂CO₃
c) KCl
d) CaCO₃
Answer: a) NaHCO₃

31. Which of the following is a transition element?
a) Iron
b) Sodium
c) Calcium
d) Chlorine
Answer: a) Iron

32. The common name for CaO is:
a) Lime
b) Quicklime
c) Slaked lime
d) Limestone
Answer: b) Quicklime

33. Which gas is released when metals react with dilute acids?
a) Oxygen
b) Hydrogen
c) Carbon dioxide
d) Nitrogen
Answer: b) Hydrogen

34. The number of neutrons in ¹²C is:
a) 6
b) 12
c) 14
d) 8
Answer: a) 6

35. Which of the following compounds is an alcohol?
a) CH₃OH
b) CH₄
c) H₂O
d) CO₂
Answer: a) CH₃OH

36. The gas responsible for acid rain is:
a) CO₂
b) SO₂
c) N₂
d) O₂
Answer: b) SO₂

37. The chemical formula of table salt is:
a) NaCl
b) KCl
c) Na₂CO₃
d) CaCl₂
Answer: a) NaCl

38. Which of the following is a base?
a) HCl
b) NaOH
c) CO₂
d) SO₂
Answer: b) NaOH

39. The type of bond in H₂O is:
a) Ionic
b) Covalent
c) Metallic
d) Hydrogen only
Answer: b) Covalent

40. The substance that speeds up a chemical reaction without being consumed is called:
a) Solvent
b) Reactant
c) Catalyst
d) Product
Answer: c) Catalyst

Section 3: Questions 41–50

Most repeated Chemistry JAMB Past Questions and Answers:

41. Which of the following is an isotope of hydrogen?
a) Deuterium
b) Oxygen
c) Carbon
d) Nitrogen
Answer: a) Deuterium

42. The gas evolved when sodium bicarbonate reacts with acid is:
a) CO₂
b) O₂
c) H₂
d) N₂
Answer: a) CO₂

43. The molar mass of H₂SO₄ is:
a) 98 g/mol
b) 100 g/mol
c) 96 g/mol
d) 102 g/mol
Answer: a) 98 g/mol

44. Which of the following is an organic compound?
a) CH₄
b) NaCl
c) H₂O
d) O₂
Answer: a) CH₄

45. The concentration of a solution is expressed in:
a) Molarity
b) Pressure
c) Temperature
d) Volume
Answer: a) Molarity

46. Which of these is a strong acid?
a) HCl
b) CH₃COOH
c) H₂CO₃
d) H₂O
Answer: a) HCl

47. The electronic configuration of Na (atomic number 11) is:
a) 1s² 2s² 2p⁶ 3s¹
b) 1s² 2s² 2p⁶ 3p¹
c) 1s² 2s² 2p⁶
d) 1s² 2s² 2p⁴ 3s²
Answer: a) 1s² 2s² 2p⁶ 3s¹

48. The compound K₂SO₄ is called:
a) Potassium sulfate
b) Potassium sulfite
c) Potassium sulfide
d) Potassium hydrogen sulfate
Answer: a) Potassium sulfate

49. The principle of fractional distillation is based on:
a) Difference in boiling points
b) Difference in solubility
c) Difference in density
d) Difference in mass
Answer: a) Difference in boiling points

50. The formula of ethanol is:
a) C₂H₅OH
b) CH₃OH
c) C₂H₆
d) C₂H₄O
Answer: a) C₂H₅OH

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