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 noble gases is commonly found in the atmosphere? Options:
  A) Xenon
  B) Neon
  C) Helium
  D) Argon
  Show Answer
  The correct answer is D .
• Question 722: Water for town supply is chlorinate to make it free from Options:
  A) bad colour
  B) bacteria
  C) temporary hardness
  D) permanent hardness
  Show Answer
  The correct answer is B .
• Question 723: For the reaction 2Fe³⁺ 2I^- $\to$ 2Fe²⁺ + I₂, which of the following statements is TRUE? Options:
  A) Fe is oxidized to Fe³⁺
  B) Fe³⁺ is oxidized to Fe²⁺
  C) I^- is oxidized to I₂
  D) I^- is reduced to I₂
  E) I^- is displacing an electron from Fe³⁺
  Show Answer
  The correct answer is C .
• Question 724: Which of the following is used to hasten the ripening of fruit? Options:
  A) Ethene
  B) Ethanol
  C) Ethyne
  D) Ethane
  Show Answer
  The correct answer is A .
• Question 725: The gas that can be collected by downward displacement of air is Options:
  A) chlorine
  B) sulphur (IV) oxide
  C) carbon (IV) oxide
  D) ammonia
  Show Answer
  The correct answer is D .
• Question 726: The product formed at the the cathode during the electrolysis of sodium chloride solution with carbon electrodes is? Options:
  A) sodium
  B) chlorine
  C) hydrogen
  D) sodium hydroxide
  E) oxygen
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  The correct answer is C .
• Question 727: The process involved in the conversion of an oil into margarine is known as? Options:
  A) hydrogenation
  B) condensation
  C) pyrolysis
  D) dehydration
  E) cracking
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  The correct answer is A .
• Question 728: When H₂S gas is passed into a solution of iron (III) chloride, the colour changes from yellow to green. This is because? Options:
  A) H_(s)S is reduced to S
  B) Fe³⁺ ions are oxidized by H_(s)S
  C) Fe³⁺ ions are oxidized Fe³⁺ ions
  D) Fe³⁺ ions are reduced to Fe²⁺ ions
  Show Answer
  The correct answer is D .
• Question 729:

  Two equal bulbs, one containing ammonia and the other nitrogen are opened mouth-to-mouth to each other at room temperature. The entropy in the mixture of gases is likely to

  Options:
  A) remain unchanged
  B) increase
  C) decrease
  D) change
  Show Answer
  The correct answer is B .
• Question 730:

  The boiling of fat and aqueous caustic soda is referred to as

  Options:
  A) hydrolysis
  B) esterification
  C) acidification
  D) saponification
  Show Answer
  The correct answer is D .