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 21:

  2H_2(g) + O_2(g) → 2H₂ O_(g)

  In the reaction above, what volume of hydrogen would be left over when 300 cm³ of oxygen and 1000 cm³ of hydrogen are exploded in a sealed tube?

  Options:
  A) 200 cm³
  B) 400 cm³
  C) 600 cm³
  D) 700 cm³
  Show Answer
  The correct answer is B .
• Question 22: When H₂S gas is passed into a solution of iron (III) chloride, the colour changes from yellow to green. This is because? Options:
  A) H_(s)S is reduced to S
  B) Fe³⁺ ions are oxidized by H_(s)S
  C) Fe³⁺ ions are oxidized Fe³⁺ ions
  D) Fe³⁺ ions are reduced to Fe²⁺ ions
  Show Answer
  The correct answer is D .
• Question 23: The IUPAC names of the compounds CH₃COOH and CH₂=CH₂ are respectively; Options:
  A) acetic acid and ethane
  B) ethanoic acid and ethene
  C) methanoic acid and ethylene
  D) ethanol and ethene
  E) acetic acid and ethylene
  Show Answer
  The correct answer is B .
• Question 24: which of the following metals will show the highest metallic character? Options:
  A) Zinc
  B) Copper
  C) Barium
  D) Calcium
  Show Answer
  The correct answer is D .
• Question 25: The nucleus of an atom contains Options:
  A) protons only
  B) neurons only
  C) protons and electrons
  D) neutrons and electrons
  E) protons and neutrons
  Show Answer
  The correct answer is E .
• Question 26: According to the kinetic theory, an increase in temperature causes the kinetic energy of particles to Options:
  A) Decrease
  B) Increase
  C) Remain constant
  D) Be zero
  Show Answer
  The correct answer is B .
• Question 27:

  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 28: Insoluble salts can be prepared by Options:
  A) titrating an alkali against an appropriate acid
  B) reacting an acid with trioxocarbonatr (IV) salt
  C) directing combination of the elements which make up the salt
  D) mixing two soluble compounds containing the metallic radical and the acidic radical
  Show Answer
  The correct answer is D .
• Question 29: The general formula of an alkyl halide (where X represents the halide) is? Options:
  A) C_nH_2n2X
  B) C_nH_2n + ₁X
  C) C_nH_2n + ₂X
  D) C_nH_2nX
  Show Answer
  The correct answer is B .
• Question 30: The atomic radius of Li, Na and K are 1: 33A, 1. 54A and 1. 96A res pectively. Which of the following explaqins this gradation in atomic radius? Options:
  A) electropositivity decreases from Li to Na to K
  B) electronegativity decreases from Li to Na to K
  C) the number of the electron shells increases from Li to Na to K
  D) the elements are in the same period
  Show Answer
  The correct answer is C .