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 931: The electronic configuration of an elements is 1s²2s²2p⁶3s²3p³. How many unpaired electrons are there in the element? Options:
  A) 5
  B) 4
  C) 3
  D) 2
  Show Answer
  The correct answer is C .
• Question 932: Oxygen-demanding waste are considered to be a water pollutant because they? Options:
  A) deplete oxygen which is necessary for the survival of aquatic organism
  B) increase oxygen which is necessary for survival of aquatic organism
  C) increase other gaseous substances which are necessary for the survival of aquatic organisms
  D) deplete other gaseous species which is necessary for the survival of aquatic organisms
  Show Answer
  The correct answer is A .
• Question 933: In which of the following are the aqueous solutions of each of the substances correctly arranged in order to decreasing acidity? Options:
  A) Ethanoic acid, milk or magnesia, sodium chloride, hydrochloric acid and sodium hydroxide
  B) Ethanoic acid, hydrochloric acid, milk of magnesia, sodium chloride and sodium chloride and sodium hydroxide
  C) Hydrochloride acid, ethanol acid, sodium chloride, milk of magnesia and sodium hydroxide
  D) Hydrochloride acid, sodium hydroxide sodium chloride, ethanol acid, and milk of magnesia
  Show Answer
  The correct answer is C .
• Question 934: Which of the following is not an alkali? Options:
  A) Ca(OH)₂
  B) NH₃
  C) NaOH
  D) Al(OH)₃
  Show Answer
  The correct answer is B .
• Question 935: Sodium chloride may be obtained from brine by Options:
  A) titration
  B) decantation
  C) distillation
  D) evaporation
  E) sublimation
  Show Answer
  The correct answer is D .
• Question 936: Hydration of ions in solution is associated with Options:
  A) absorption of heat
  B) reduction of heat
  C) conduction of heat
  D) liberation of heat
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  The correct answer is D .
• Question 937: What happens when zinc rod is immersed in copper (II) tetraoxosulphate (VI) solution/ Options:
  A) The blue colour of the solution disappears
  B) Electrons flow from copper to zinc
  C) The zinc rod remain undissolved
  D) The copper generate more copper ions
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  The correct answer is A .
• Question 938: The reaction between ammonia and ethyl ethanoate produces Options:
  A) propanol and ethanamide
  B) propanol and propanamide
  C) ethanol and propanamide
  D) ethanol and ethanamide
  Show Answer
  The correct answer is D .
• Question 939: The chemicals used to soften hard water involves the addition of Options:
  A) insoluble sodium compounds which from soluble solutions of calcium and magesium
  B) solube soudium compounds which from soluble solutions of calcium and magnesium ions
  C) solube sodium compounds which from insoluble precipitates of calcium and magnesium ions
  D) insoluble precipitates of calcium and magnesium ions
  Show Answer
  The correct answer is C .
• Question 940:

  H_2(g) + Br_2(g) → 2HBr_(g)

  The above reaction is carried out at 25^oC. ΔH is -72 kJ mol^-1 and ΔS is - 106 J mol^-1K^-1, the reaction will

  Options:
  A) not proceed spontaneously at the given
  B) proceed spontaneously at the given temperature
  C) proceed in the reverse direction at the given temperature
  D) proceed spontenously at lower temperature
  Show Answer
  The correct answer is A .