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 11: Hardness of water is mainly due to the presence of Options:
  A) calcium hydroxide or magnesium hydroxide
  B) calcium trioxocarbonate (IV) or calcium tetraoxosulphate (VI)
  C) sodium hydroxide or magnesium ydroxide
  D) calcium chloride or sodium chloride salts
  Show Answer
  The correct answer is B .
• Question 12:

  

  In the diagram above which of the cures illustrates Arrhenius' law?

  Options:
  A) Y
  B) Z
  C) R
  D) X
  Show Answer
  The correct answer is D .
• Question 13:

  Which of the following reactions is (are) feasible?

  I Br ₍₁₎ + 2CI _2(aq) 2Br _(aq) + CI _2(g)

  Ll 21 _(aq) + Br ₂₍₁₎ 2Br _(aq) + 1 _2(s)

  Lll 2F _(aq) + CI _2(g) 2CI _(aq) + F _2(g) IV 2F _(aq) + Br ₂₍₁₎ 2Br _(aq) + F _2(g)

  Options:
  A) l
  B) ll
  C) l and lll
  D) lll and lV
  Show Answer
  The correct answer is B .
• Question 14:

  What is the valency of an element with the electronic configuration 2, 8, 7?

  Options:
  A) 7
  B) 1
  C) 2
  D) 3
  Show Answer
  The correct answer is B .
• Question 15:

  The process by which salt and water reacted in a limited way to form an acid or abase is?

  Options:
  A) Neutral process
  B) Basic acidic process
  C) Hydrolysis
  D) Sublimation
  Show Answer
  The correct answer is C .
• Question 16:

  When anhydrous cobalt chloride paper is exposed to water, what color change is observed?

  Options:
  A) From pink to blue
  B) From white to blue
  C) From blue to white
  D) From blue to pink
  Show Answer
  The correct answer is D .
• Question 17:

  

  Use the options above to answer this question. Which is the structural formula for pent-2-enoic acid?

  Options:
  A) A
  B) B
  C) C
  D) D
  Show Answer
  The correct answer is C .
• Question 18:

  Cu²⁺_(aq) + 4NH_3(g) ↔ [Cu(NH₃)₄]²⁺_(aq)

  In the reaction above, what is the effect of precipitating Cu²⁺_(aq) as CuS_(s)?

  Options:
  A) NH_3(g) concentration will decrease
  B) more NH_3(g)
  C) The equilibrium will shift to the right
  D) There will be no effect
  Show Answer
  The correct answer is C .
• Question 19: Which of the following methods can be used to obtain pure water from a mixture of sand, water and methanoic acid? Options:
  A) netralization with NaOHfoolowed by filtration
  B) neutralization with NaOH followed by distillation
  C) fractional distillation
  D) filtration followed by distillation
  Show Answer
  The correct answer is D .
• Question 20: Which of the following will change when a catalyst is added to a chemical reaction? Options:
  A) The activation energy
  B) The potential energy of the reactants
  C) The heat of the reaction
  D) the potential energy of the product
  Show Answer
  The correct answer is A .