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 821: What mass of a divalent metal M (atomic mass = 40) would react with excess hydrogen gas measured at S.T.P? Options:
  A) 8.0 g
  B) 4.0 g
  C) 0.8 g
  D) 0.4 g
  Show Answer
  The correct answer is D .
• Question 822:

  When a solid substance disappears completely as a gas on heating, the substance is said to have undergone?

  Options:
  A) Sublimation
  B) Crystallization
  C) Distillation
  D) Evaporation
  Show Answer
  The correct answer is A .
• Question 823:

  Which of the following does not support the fact that air is a mixture?

  Options:
  A) the constituents of air are in a fixed proportion by mass
  B) it cannot be represented with a chemical formula
  C) the constituents of air can be separated by physical by physical means
  D) none of the above
  Show Answer
  The correct answer is A .
• Question 824:

  What is the empirical formula of a compound containing 40.00% carbon, 6.67% hydrogen, and 53.33% oxygen by mass?

  Options:
  A) C${}_4$H${}_8$O${}_4$
  B) CH${}_2$O
  C) C${}_2$H${}_4$O${}_2$
  D) C${}_3$H${}_6$O${}_3$
  Show Answer
  The correct answer is B .
• Question 825:

  Alkanes are used mainly?

  Options:
  A) in the textile industry
  B) in the hydrogenation of oils
  C) as domestic and industrial fuels
  D) as fine chemicals
  Show Answer
  The correct answer is C .
• Question 826: 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 827:

  Which of the following gases will diffuse fastest when passed through a porous plug?

  [H = 1, C = 12, N = 14, O = 16]

  Options:
  A) Propane
  B) Oxygen
  C) Methane
  D) Ammonia
  Show Answer
  The correct answer is C .
• Question 828: In the reaction Fe + Cu²⁺ $\to$ Fe²⁺ + Cu,iron displaces copper ions to from copper. This is due to the fact that Options:
  A) irn is in the metallic from while the copper is in the ionic from
  B) the atomic weight of copper is greater than that of iron
  C) copper is greater than iron
  D) copper metal has more electrons than iron metal
  E) iron is higher in the electrochemical series than copper
  Show Answer
  The correct answer is E .
• Question 829:

  If 100 cm³ of oxygen pass through a porous plug in 50 seconds, the time taken for the same volume of hydrogen to pass through the same porous plug is?

  (O = 16, H = 1)

  Options:
  A) 10.0 s
  B) 12.5 s
  C) 17.7 s
  D) 32.0 s
  Show Answer
  The correct answer is B .
• Question 830: A piece of filter paper moistened with lead (ll) ethanoate solution turns black when the paper is dropped into a gas likely to be Options:
  A) sulphur (VI) oxide
  B) hydrogen chloride
  C) sulphur (VI) oxide
  D) hydrogen sulphide
  Show Answer
  The correct answer is D .