Chemistry Exam Past Questions and Answers | JAMB, WAEC and NECO

Chemistry is the study of the substances that make up matter. It looks at their properties, how they react with each other, and how these reactions can create new substances.

• Question 731:

  Which trace gas in the atmosphere plays a significant role in the greenhouse effect?

  Options:
  A) Oxygen
  B) Argon
  C) Carbon dioxide
  D) Nitrogen
  Show Answer
  The correct answer is C .
• Question 732: An oxide XO₂ has a vapour density of 32. What is the atomic mass of X? Options:
  A) 32
  B) 20
  C) 14
  D) 12
  Show Answer
  The correct answer is A .
• Question 733:

  What is the empirical formula of a compound containing 40.00% carbon, 6.67% hydrogen, and 53.33% oxygen by mass?

  Options:
  A) C${}_4$H${}_8$O${}_4$
  B) CH${}_2$O
  C) C${}_2$H${}_4$O${}_2$
  D) C${}_3$H${}_6$O${}_3$
  Show Answer
  The correct answer is B .
• Question 734: The scale of a chemical balance is made of iron plate and coated with copper electrolytically because Options:
  A) iron is less susceptible to corrosion than copper
  B) copper is twice as less susceptitible to corrosion as iron
  C) copper is less susceptible to corrosion than iron
  D) copper and iron are equally susceptible to corrosion
  Show Answer
  The correct answer is C .
• Question 735:

  What quantity of aluminium is deposited when a current of 10A is passed through a solution of an aluminium salt for 1930s?

  [Al = 27, F = 96500 C mol ^-1]

  Options:
  A) 0.2 g
  B) 1.8 g
  C) 5.4 g
  D) 14.2 g
  Show Answer
  The correct answer is B .
• Question 736: Safety matches contain sulphur and? Options:
  A) potassium trioxochlorate (V)
  B) potassium trioxonitrate (V)
  C) charcoal
  D) phosphorus sulphide
  Show Answer
  The correct answer is D .
• Question 737:

  What current in amperes will deposit 2.7g of aluminium in 2 hours?

  [Al = 27, F = 96 500 C mol^-1]

  Options:
  A) 32
  B) 8
  C) 4
  D) 16
  Show Answer
  The correct answer is C .
• Question 738: Haematite is an ore of Options:
  A) zinc
  B) lead
  C) iron
  D) copper
  Show Answer
  The correct answer is C .
• Question 739: A rock sample was added to cold dilute HNO₃. The gas evolved was passed into a solution of acidified K₂Cr₂O₇ and the solution turned green. The sample contains Options:
  A) Cl^-
  B) NO₃^-
  C) SO₃^2-
  D) SO₄^2-
  Show Answer
  The correct answer is C .
• Question 740:

  H₃PO_4(aq) + H₂O_(l) ↔ H₂PO₄^-_(aq) + H₃O⁺_(aq)

  ΔH = -13kJ at 298K

  In the reaction above, an increase in temperature would

  Options:
  A) slow downthe reverse reaction
  B) have no effect on the reaction
  C) favour the reverse reaction
  D) favour the forward reaction
  Show Answer
  The correct answer is C .