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 471: Two hydrocarbons X and Y were treated with bromine water. X decolorised the solution and Y did not not. Which class of compound does Y belong? Options:
  A) Benzene
  B) Alkynes
  C) Alkenes
  D) Alkanes
  Show Answer
  The correct answer is D .
• Question 472: Sodium hydroxide is prepared commercially from sodium chloride solution by? Options:
  A) electrolysis using mercury as cathode
  B) hydrolysis in steam using a catalyst
  C) electrolysis using iron as anode
  D) treating sodium chloride with ammonia and carbon (IV) oxide
  Show Answer
  The correct answer is A .
• Question 473:

  

  The above diagram gives the potential energy profile of the catalyst and uncatalysed reactions of X_(g) + Y_(g) → XY_(g). Deduce the respective activation energies in KJ of the catalysed and uncatalysed reverse reactions: XY(g) → X_(g) + Y_(g)

  Options:
  A) 300, 500
  B) 500, 300
  C) -300, -500
  D) -500, -300
  Show Answer
  The correct answer is A .
• Question 474:

  ²²⁶₈₈Ra → ^x₈₆Rn + α - particle

  What is the value of x in the nuclear reaction above?

  Options:
  A) 220
  B) 222
  C) 226
  D) 227
  Show Answer
  The correct answer is B .
• Question 475:

  A compound contains 31.91% potassium, 28.93% chlorine and the rest oxygen. What is the chemical formula of the compound?

  [K = 39, Cl = 35.5, O = 16]

  Options:
  A) KClO₄
  B) KClO
  C) KClO₂
  D) KClO₃
  Show Answer
  The correct answer is D .
• Question 476: The presence of nitrogen in air is to slow down Options:
  A) respiration and combustion
  B) combustion and corrosion
  C) corrosion and respiration
  D) respiration and transpiration
  Show Answer
  The correct answer is B .
• Question 477: When each of the nitrates of Potassium, Magnesium and iron is heated, Options:
  A) all the nitrates decompose to their oxides
  B) the nitrate of magnesium gives the nitrite and oxygen
  C) the nitrates of iron magnesium and iron give the oxides
  D) the nitrate of iron gives the nitrite and oxygen
  E) the nitrate of the magnesium is not decomposed
  Show Answer
  The correct answer is C .
• Question 478:

  In the extraction of iron, hot air is introduced into the blast furnacethrough?

  Options:
  A) valves
  B) open-hearths
  C) arcs
  D) tuyeres
  Show Answer
  The correct answer is D .
• Question 479: The hydrocarbon used in the production of styrene is Options:
  A) ethyne
  B) propyne
  C) ethane
  D) ethene
  Show Answer
  The correct answer is D .
• Question 480: Potassium tetraoxomanganate (VII) is often added to impure water to? Options:
  A) reduce organic impurities
  B) reduce inorganic impurities
  C) destroy bacteria and algae
  D) remove permanent hardness
  Show Answer
  The correct answer is C .