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 721: Which of the following will react further with oxygen to form higher oxide? Options:
  A) NO and H₂O
  B) CO and CO₂
  C) SO₂ and NO
  D) CO₂ and H₂O
  Show Answer
  The correct answer is C .
• Question 722: When carbondioxide is bubbled into limewater a white precipitate is formed. If the passage of the gas is continued, the precipitate disappears. The reason for this is Options:
  A) calcium carbonate is formed which on reaction dissolves
  B) calcium hydrogen carbonate is precipitated and then dissolves
  C) calcium carbonate is formed which on reaction with further carbondioxide forms solube calcium hydrogen carbonate
  D) concentration of the solution has occurred with the deposition of calcium hydroxide
  E) the solution has become saturated and solid carbondioxide has been deposited
  Show Answer
  The correct answer is C .
• Question 723:

  Na₂S₂O_3(aq) + 2HCl_(aq) → 2NaCl_(aq) + H₂O_(l)

  Which of the following would introduce the greatest increase in the rate of the chemical reaction above?

  Options:
  A) An increase in temperature and decrease in the concentration of the reactant
  B) A decrease in the volume and increase in the pressure of the reactant
  C) A decrease in the temperature and an incease in the concentration of the reactant
  D) An increase in temperature and an increase in the concentration of the reactant
  Show Answer
  The correct answer is D .
• Question 724: The importance of sodium aluminate (III) in the treatment of water is to Options:
  A) cause coagulation
  B) neutralize acidity
  C) prevent goitre and tooth decay
  D) kill germs
  Show Answer
  The correct answer is A .
• Question 725: Mineral acids are usually added to commercial hydrogen peroxide to Options:
  A) oxidize it
  B) decompose it
  C) minimize its decomposition
  D) reduce it to water and oxygen
  Show Answer
  The correct answer is C .
• Question 726: Ammonium chloride can be separated from its mixture with common salt by Options:
  A) Distillation
  B) Evaporation
  C) Decantation
  D) Sublimation
  Show Answer
  The correct answer is D .
• Question 727: The metal that liberates hydrogen from cold water in bubbles only is Options:
  A) Na
  B) K
  C) Ca
  D) Al
  Show Answer
  The correct answer is C .
• Question 728:

  

  In the graph above, the activation energy of the catalyzed reaction is

  Options:
  A) 100KJ
  B) 300KJ
  C) 250KJ
  D) 200KJ
  Show Answer
  The correct answer is A .
• Question 729: The radioisotope used in industrial radiography for the rapid checking of faults in welds and casting is Options:
  A) Phosphorus-32
  B) Cobalt-60
  C) Carbon-14
  D) Iodine-131
  Show Answer
  The correct answer is B .
• Question 730: The major component of the slag from the production of iron is? Options:
  A) an alloy of calcium and iron
  B) coke
  C) impure iron
  D) calcium trioxosilicate (IV)
  Show Answer
  The correct answer is B .