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 441: The dissolution of common salt in water is a physical change because Options:
  A) the salt can be obtained by crystallization
  B) the salt can be recovered by the evaporation of water
  C) heat is not generated during mixing
  D) the solution will not boil at 100^oC
  Show Answer
  The correct answer is C .
• Question 442:

  What is the mass percentage of carbon (C) in methane (CH4)? (The molar mass of carbon is approximately 12 g/mol.)

  Options:
  A) 25%
  B) 12%
  C) 75%
  D) 50%
  Show Answer
  The correct answer is C .
• Question 443: An electron can be added to a halogen atom to form a halide ion with Options:
  A) 2 valence electrons
  B) 3 valence electrons
  C) 7 valence electrons
  D) 8 valence electrons
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  The correct answer is D .
• Question 444: In the reaction of oxygen with hydrogen to produce water, which of the following statements is true? Options:
  A) One atom of hydrogen reacts with two atoms of oxygen to give one molecule of water
  B) Two atoms of hydrogen react with two atoms of oxygen to give two molecules of water
  C) One molecule of oxygen reacts with one molecule of hydrogen to give two molecules of water
  D) One molecule of hydrogen reaccts with two molecules of oxygen to give three molecules of water
  E) One molecule of oxygen reacts with two molecules of hydrogen to give two molecules of water
  Show Answer
  The correct answer is E .
• Question 445: Ethene when passed into concentrated H₂SO₄ is rapidly absorbed. The product is diluted with water and then warmed to produce? Options:
  A) ethanol
  B) diethyl ether
  C) ethanal
  D) diethyl sulphate
  Show Answer
  The correct answer is A .
• Question 446: You are provided with five gas jars containing SO₂, CO₂, H₂, CO and NO respectively. Select a test from A to E which will identify ANY ONE of the gases completely Options:
  A) pass each gas into lime water
  B) pass each gas into water and test with litmus paper
  C) pass each gas into concentrated sulphuric acid
  D) expose each gas to atmospheric air
  E) expose each gas to fumes of hydrogen chloride
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  The correct answer is A .
• Question 447: 2H₂S_(g) + SO_2(g) → 3S_(s) + 2H₂O_(I). The above reaction is? Options:
  A) a redox reaction H₂S is the oxidant and SO₂ is the reductant
  B) a redox reaction in which SO₂ is the oxidant and H₂S is the reductant
  C) not a redox reaction because there is no oxidant in reaction equation
  D) not a redox because there is no reductant in the reaction equation
  Show Answer
  The correct answer is B .
• Question 448:

  A dense white fume is formed when ammonia gas reacts with

  Options:
  A) O_2(g)
  B) H_2(g)
  C) Cl_2(g)
  D) HCl_(g)
  Show Answer
  The correct answer is D .
• Question 449:

  Which of the following changes is physical?

  Options:
  A) Adding iron filing to aerated water
  B) Adding sodium metal to water
  C) Cooling a solution of Iron (II) sulphate to obtain the hydrated salt
  D) Cooling water to obtain ice
  E) Burning the domestic gas (Utilgas) for cooking
  Show Answer
  The correct answer is D .
• Question 450: Crude copper could be purified by the electrolysis of concentrated copper (II) chloride if the crude copper is? Options:
  A) made both the anode and the cathode
  B) made the cathode
  C) made the anode
  D) dissolved in the solution
  Show Answer
  The correct answer is C .