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 2041: What is the formula of sodium gallate if gallium (Ga)shows an oxidation number of + 3? Options:
  A) NaGaO₃
  B) Na₂Ga(OH)₃
  C) NaGa(OH)₃
  D) NaGa(OH)₄
  E) NaGaO
  Show Answer
  The correct answer is D .
• Question 2042: On heating, under suitable conditions, 1 litres of monoatomic gas,X, combines with 1¹/₂ litres of an oxide, What is the formula of the oxide. Options:
  A) XO₃
  B) X₂O₃
  C) X₃O₂
  D) XO₂
  E) None of the above
  Show Answer
  The correct answer is B .
• Question 2043: If d represents the density of a gas and K is a constant, the rate of gaseous diffusion r is related to d by the equation? Options:
  A) r = k/√d
  B) r = kd
  C) r =k/d
  D) r = k √d
  Show Answer
  The correct answer is A .
• Question 2044: When pollen grains are suspended in water and viewed through a microscope, they appear to be in a state of constant but erratic motion. This is due to? Options:
  A) convection currents
  B) small changes
  C) small changes in temperature
  D) a chemical reaction between the pollen grain and water
  E) the bombardment of the pollen grains by molecules of water
  Show Answer
  The correct answer is E .
• Question 2045: The chlorinated alkane often used industrially to remove grease is Options:
  A) tetrachloromethane
  B) chloromethane
  C) trichloromethane
  D) dichlorometane
  Show Answer
  The correct answer is A .
• Question 2046: The iron (III) oxide impurity in bauxite can be removed by? Options:
  A) Fractional crystallization in acid solution
  B) dissolution in sodium hydroxide and filtration
  C) extraction with concentrated ammonia and reprecipitation
  D) electroysis of molten mixture
  Show Answer
  The correct answer is B .
• Question 2047: According to Charle's law, the volume of a gas becomes zero at Options:
  A) −100°c
  B) −273°c
  C) −373°c
  D) 0°c
  Show Answer
  The correct answer is B .
• Question 2048: In which of the following reactions is sulphur dioxide acting as an oxidizing agent? Options:
  A) SO ₂ + 2HNO₃ →H₂SO₄ + NO₂ + Heat
  B) 2SO₂ + 2H₂O + O₂→ 2H₂SO₄
  C) SO₂ + 2H₂O + CI₂→ H₂SO₄ + 2HCI
  D) SO₂ + 2H₂S → 3S + 2H₂O
  E) SO₂ + H₂O → H₂SO₃
  Show Answer
  The correct answer is D .
• Question 2049:

  Cr₂O₇ + 6Fe²⁺ + 14H⁺ → 2Cr3+ + 6Fe³⁺ + 7H₂O. In the above, the oxidation number of chromium changed from?

  Options:
  A) +7 to +3
  B) +6 to +3
  C) +5 to +3
  D) -2 to +3
  Show Answer
  The correct answer is A .
• Question 2050: How many cations will be produced from a solution of potassium aluminium tetraoxosulphate (VI)? Options:
  A) 3
  B) 4
  C) 1
  D) 2
  Show Answer
  The correct answer is D .