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 421: What happens when the nitrates of potassium, calcium, zinc and copper are separately heated? Options:
  A) All the nitrate will decompose to their respective metals
  B) The nitrates of calcium and potassium will decomposes to their nitrites
  C) Only copper nitrate decomposes to the metal
  D) Only the nitrates of zinc and copper will decompose to their oxides
  E) The nitrates of calcium, zinc and copper decompose to their oxides
  Show Answer
  The correct answer is E .
• Question 422: Consider the following exothermic reaction 2SO₂(g) + O₂(g) = 2SO₃ (g) . If the temperature of the reaction is reduced from 800_oC to 500_oC, and no other change takes place, then Options:
  A) the reaction rate increases
  B) concentration of SO₃ decreases
  C) concentration of SO₃ increases
  D) SO₂ gas becomes unreactive
  E) O₂ gas becomes unreactive
  Show Answer
  The correct answer is C .
• Question 423:

  Which of the following sets of operation will completely separate a mixture of sodium chloride, sand and iodine?

  Options:
  A) addition of water, filtration, evaporation to dryness and sublimation
  B) filtration, evaporation to dryness, addition of water and sublimation
  C) sublimation, filtration, evaporation and addition of water
  D) sublimation, addition of water, filtration and evaporation to dryness
  Show Answer
  The correct answer is A .
• Question 424:

  A binary compound of oxygen with another element is referred to as?

  Options:
  A) Oxide
  B) Element
  C) Carbon
  D) Nitrogen
  Show Answer
  The correct answer is A .
• Question 425: The solvent used for removing grease stain is Options:
  A) turpentine
  B) ammonia solution
  C) ethanol
  D) solution of borax in water
  Show Answer
  The correct answer is B .
• Question 426: The oxidation number of manganese in KMnO₄ is? Options:
  A) +1
  B) +3
  C) +5
  D) +7
  E) +2
  Show Answer
  The correct answer is D .
• Question 427:

  How many pi ($\pi$) bonds are there in an alkene with six carbon atoms?

  Options:
  A) 4
  B) 6
  C) 5
  D) 3
  Show Answer
  The correct answer is D .
• Question 428: The difference between colloides and and suspensions is brought out clearly by the fact that while colloids? Options:
  A) do not scatter light, suspensions do
  B) can be separated by filtration, suspension cannot be so separated
  C) can be separated by a membrane, suspensions cannot
  D) do not settle out on standing, suspensions do
  Show Answer
  The correct answer is D .
• Question 429:

  Which of the following gases will rekindle a brightly splint?

  Options:
  A) NO${}_2$
  B) NO
  C) N${}_2$O
  D) CL${}_2$
  Show Answer
  The correct answer is C .
• Question 430: Which of the following is a example of a chemical change? Options:
  A) Dissoultion of salt in water
  B) Rusting of iron
  C) Melting of ice
  D) Separating a mixture by distillation
  Show Answer
  The correct answer is B .