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 271: Ethene is prepared industrially by Options:
  A) Reforming
  B) Polymerization
  C) Distillation
  D) Cracking
  Show Answer
  The correct answer is D .
• Question 272: The characteristics reaction of carbonyl compounds is? Options:
  A) substitution
  B) elimination
  C) addition
  D) saponfication
  Show Answer
  The correct answer is C .
• Question 273: When glowing splint is inserted into the mouth of a jar containing a gas, the splint is extinguished. The gas gives a white precipitate when passing into barium hydroxide. The gas is? Options:
  A) methane
  B) hydrogen chloride
  C) hydrogen
  D) nitrogen
  E) carbondioxide
  Show Answer
  The correct answer is E .
• Question 274: The nitrogen gas obtained by burning an excess of phosphorus in air has a density higher than the nitrogen from nitrogen compounds because the nitrogen from air is contaminated with? Options:
  A) some unburnt phosporus
  B) P₂O₅ vapour
  C) some oxygen
  D) rare gases
  E) carbondioxide
  Show Answer
  The correct answer is D .
• Question 275:

  The oxidation state(s) of nitrogen in ammonium nitrite is/are

  Options:
  A) -3, +3
  B) +5
  C) -3, +5
  D) -3
  Show Answer
  The correct answer is A .
• Question 276:

  When a substance is oxidized, it

  Options:
  A) Loses electrons
  B) Gains oxygen atoms
  C) Gains electrons
  D) Loses protons (H+ ions)
  Show Answer
  The correct answer is A .
• Question 277:

  In the laboratory preparation of oxygen, the gas cannot be collected by displacement of air because

  Options:
  A) the density of oxygen is greater than that of air
  B) the density of air is nearly the same as that of oxygen
  C) oxygen is a component of air
  D) air is an impure substance
  Show Answer
  The correct answer is A .
• Question 278: What current in ampere will deposit 0.27g of aluminium in 2 hours? [Al = 27, F = 96500C]. Options:
  A) 3.2
  B) 8
  C) 0.4
  D) 16
  Show Answer
  The correct answer is C .
• Question 279: The minimum volume of oxygen required for the complete combustion of a mixture of 10cm ³ of CO and 15 cm ³ of H ² is Options:
  A) 25.0cm³
  B) 12.5 cm³
  C) 10.0 cm³
  D) 5.0cm³
  Show Answer
  The correct answer is C .
• Question 280: CH₃CH₂Cl + KCN → CH₃CH₂CN + KClIn the reaction above, the cyanide is Options:
  A) hydrophobic
  B) hydrophilic
  C) nucleophilic
  D) electrophilic
  Show Answer
  The correct answer is C .