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 2211: Calculate the number of moles of HCl present in 20cm³ of a 0.75M solution of the acid Options:
  A) 0.015 mole
  B) 0.038 mole
  C) 3.800 moles
  D) 1.500 moles
  Show Answer
  The correct answer is A .
• Question 2212: Which of the following substance is a mixture? Options:
  A) Granulated sugar
  B) Sea-water
  C) Sodium chloride
  D) Iron fillings
  Show Answer
  The correct answer is B .
• Question 2213: The chemical reaction which takes place at the anode (positive electrode) in electrolysis is? Options:
  A) oxidation
  B) hydrolysis
  C) dissociation
  D) reduction
  E) disproportionation
  Show Answer
  The correct answer is A .
• Question 2214:

  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 2215:

  Which of the following substances is a mixture?

  Options:
  A) Granulated sugar
  B) Seawater
  C) Sodium chloride
  D) Iron filling
  Show Answer
  The correct answer is B .
• Question 2216: Solid sodium hydroxide on exposure to air absorbs a gas and ultimately gives another alkaline substance with the molecular formula? Options:
  A) NaOH.H₂O
  B) NaOH.N₂
  C) Na₂CO₃O
  D) NaHCO₃
  E) NaNO₃O
  Show Answer
  The correct answer is C .
• Question 2217:

  2SO_2(g) + O_2(g) $⟺$2SO_3(g)

  $△H=-395.7kJmo{l}^{-1}$

  In the reaction above, the concentration of 2SO_3(g) can be in creased by

  Options:
  A) decreasing the pressure
  B) decreasing the temperature
  C) the addition of catalyst
  D) increasing the temperature
  Show Answer
  The correct answer is B .
• Question 2218: A sample of an oxide of mercury weighed 1.00g. When this was heated, oxygen was given off, and 1.00g of mercury metal only was left. What is the formula of the oxide? Options:
  A) Hg₂O
  B) HgO₂
  C) HgO₂
  D) HgO
  E) None of the above
  Show Answer
  The correct answer is E .
• Question 2219: Helium atoms are chemically unreactive because Options:
  A) there are no electrons around the nucleus
  B) the number of protons equals the number of electrons
  C) there are equal number of protons and neutrons in the nucleus
  D) the outer electron shell is completely filled
  E) the atoms contain only protons
  Show Answer
  The correct answer is D .
• Question 2220: The efficiency of petrol as a fuel in high-compression internal combustion engines improves with an increase in the amount of? Options:
  A) branched chain alkanes
  B) straight chain alkanes
  C) cycloalkanes
  D) halogenated hydrocarbons
  Show Answer
  The correct answer is A .