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 1831:

  A colourless organic compound X was burnt in excess air to give two colourless and odourless gases, Y and Z, as products. X does not decolorize blue bromine vapour, Y turns lime milky while Z gives a blue colour with copper (ll) tetraoxosulphate (IV).

  Y and Z are respectively?

  Options:
  A) CO₂ and NH₃
  B) CO and NH₃
  C) SO₂ and H₂O
  D) CO₂ and H₂O
  E) SO₂ and NH₃
  Show Answer
  The correct answer is D .
• Question 1832:

  ZnO_(s) + CO_(g) → Zn_(s) + CO_2(g)

  In the reaction above, Zinc has been

  Options:
  A) decomposed
  B) displaced
  C) oxidized
  D) reduced
  Show Answer
  The correct answer is D .
• Question 1833: An example of element that can catenate is Options:
  A) bromine
  B) nitrogen
  C) chlorine
  D) carbon
  Show Answer
  The correct answer is D .
• Question 1834:

  2H_2(g) + O_2(g) → 2H₂ O_(g)

  In the reaction above, what volume of hydrogen would be left over when 300 cm³ of oxygen and 1000 cm³ of hydrogen are exploded in a sealed tube?

  Options:
  A) 200 cm³
  B) 400 cm³
  C) 600 cm³
  D) 700 cm³
  Show Answer
  The correct answer is B .
• Question 1835:

  A solution X on mixing with AgNO₃ solution, gives a white precipitate solution in NH₃. A Solution Y, when added to X, also gives a white precipiate which is soluble on boiling. Solution Y contains?

  Options:
  A) Ag⁺ ion
  B) Pb²⁺ ion
  C) Pb⁴⁺ ion
  D) Zn²⁺ ion
  E) Al³⁺ ion
  Show Answer
  The correct answer is B .
• Question 1836: What is observed when aqueous solutions of each of tetraoxosulphate (VI) acid, potassium trioxoiodate (V) and potassium iodide are mixed together? Options:
  A) A white precipitate is formed
  B) A green precipitate is formed
  C) The mixture remains colourless
  D) The mixture turns reddish brown
  Show Answer
  The correct answer is D .
• Question 1837: A compound contains 40.0% carbon, 6.7% hydrogen and 53.3% oxygen. If the molar mass of the compound is 180, Find the molecular formula [H = 1, C = 12, O = 16) Options:
  A) CH₂O
  B) C₃H₆O₃
  C) C₆H₁₂O₆
  D) C₆H₁₂O₃
  Show Answer
  The correct answer is C .
• Question 1838: Which of the following equations represents an oxidizing action of sulphur dioxide? Options:
  A) SO₂ + 2HNO₂ → H₂SO₄ + 2NO₂ + heat
  B) 2SO₂ + 2H₂O + O₂ → 2H₂SO₄
  C) SO₂ + 2H₂O + CI₂ → H₂SO₄ + 2HCI
  D) SO₂ + 2H₂S → 3S + 2H₂O
  E) K₂Cr₂O₇ + H₂SO₄ + 3SO₂ → K₂SO₄ + Cr₂(SO₄)₃ + H₂O
  Show Answer
  The correct answer is D .
• Question 1839:

  Methanoic acid mixes with water in all proportions and has about the same boiling point as water. Which of the following methods would you adopt to obtain pure water from a mixture of Sand, water and methanoic acid?

  Options:
  A) Fractional distillation
  B) Filtration followed by distillation
  C) Neutralization with sodium hydroxide followed by distillation
  D) Neutralization with sodium hydroxide followed by filtration
  Show Answer
  The correct answer is B .
• Question 1840: The polymer used in making car rear lights is Options:
  A) perspex
  B) bakeelite
  C) polystyrene
  D) polyacrylonitrile
  Show Answer
  The correct answer is A .