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 1261:

  In the upper atmosphere, the ultra-violet light breaks off a free chlorine atom from chlorofluorocarbon molecule. The effect of this is that the free chlorine atom will

  Options:
  A) be very reactive and will attack ozone
  B) be non-reactive and will not attack ozone
  C) not change the level of ozone in the atmosphere
  D) increase the level of ozone in the atmosphere
  Show Answer
  The correct answer is A .
• Question 1262: The reaction Mg + H₂O → MgO + H₂ takes place only in the presence of? Options:
  A) excess Mg ribbon
  B) excess cold water
  C) very hot water
  D) steam
  Show Answer
  The correct answer is D .
• Question 1263: A fixed mass of gas a volume of 92cm³ at 3°C. When will be its volume at 18C if the pressure remains constant? Options:
  A) 15.3cm³
  B) 87.3cm³
  C) 2.0cm³
  D) 97.0cm³
  Show Answer
  The correct answer is D .
• Question 1264: The processes which return carbon (IV) oxide to the atmosphere include Options:
  A) respiration, decay and combustion
  B) photosynthesis, respiration and transpiration
  C) ozone depletion, combustion and decay
  D) photosynthesis, decay and respiration
  Show Answer
  The correct answer is A .
• Question 1265: The droplets of water observed around a bottle of milk taken out of the refrigerator is due to the fact that the Options:
  A) water vapour in the air around the bottle gains some energy from the bottle
  B) temperature of the milk drops as it loses heat into the surroundings
  C) saturated vapour pressure of the milk is equal to the atmospheric pressure
  D) water vapour in the air around the bottle loses some of its energy to the bottle
  Show Answer
  The correct answer is D .
• Question 1266: What is the oxidation number of Z in K₃ZCl₆? Options:
  A) -3
  B) +3
  C) -6
  D) +6
  Show Answer
  The correct answer is B .
• Question 1267: Which of the following ions is a pollutant in drinking water even in trace amounts? Options:
  A) Ca²⁺
  B) Hg²⁺
  C) Mg²⁺
  D) Fe²⁺
  Show Answer
  The correct answer is B .
• Question 1268: A difference between chemical and physical change is that in a chemical change Options:
  A) oxygen is consumed
  B) heat is supplied
  C) the reversible process occurs
  D) a new substance is formed
  Show Answer
  The correct answer is D .
• Question 1269:

  The type of bonding in [Cu(NH${}_3$)${}^4$]${}^{2+}$ is 

  Options:
  A) coordinate
  B) electrovalent
  C) metallic
  D) covalent
  Show Answer
  The correct answer is A .
• Question 1270:

  MnO₂ + 2CI^- + 4H⁺ → MnO²⁺ + CI₂ + 2H₂O.

  The changes is oxidation numbers when the manganese, chloride and hydrogen ions react according to the above equation are respectively?

  Options:
  A) 2, 2, 4
  B) -1, -2, 4
  C) -2, 1, 0
  D) 2, 4, 0
  Show Answer
  The correct answer is C .