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 161:

  200 cm³ of air was passed over heated copper in a syringe several times to produce copper (II) oxide.

  When cooled, the final volume of air recorded was 158cm³. Estimate the percentage of oxygen in the air?

  Options:
  A) 31%
  B) 27%
  C) 21%
  D) 19%
  Show Answer
  The correct answer is C .
• Question 162:

  Calculate the volume in cm³ of oxygen evolved as s.t.p. when a current of 5 A is passed through acidified water for 193s

  {F = 96500 Cmol^-1, Molar volume of a gas at s.t.p. = 22.4 dm³}

  Options:
  A) 224.000 dm³
  B) 0.056 dm³
  C) 0.224 dm³
  D) 56.000 dm³
  Show Answer
  The correct answer is B .
• Question 163: When 50cm² of a saturated solution of sugar of molar mass 342 g at 40^oC was evaporated to dryness, 34.2g of dry solid was obtained. The solubility of sugar at 40^oC is Options:
  A) 2.0 mol dm^-3
  B) 3.5 mol dm^-3
  C) 7.0 mol dm^-3
  D) 10.0 mol dm^-3
  Show Answer
  The correct answer is A .
• Question 164:

  

  The IUPAC nomenclature of the structure is

  Options:
  A) 3-chloro-3-methylbutane
  B) 2,2,-dichloro-3-methylbutane
  C) 3-methylchlorobutane
  D) 2-chloro-2-methylbutane
  Show Answer
  The correct answer is D .
• Question 165: 100 cm³ of oxygen is made to react with 50 cm ³ of hydrogen, and the whole reaction mixture was then passed through anhydrous calcium chloride. What is the volume of gas left? Options:
  A) 5 cm³
  B) 25 cm³
  C) 50 cm³
  D) 75 cm³
  E) 100 cm³
  Show Answer
  The correct answer is D .
• Question 166: Polystyrene is widely used as packaging materials for fragile objects during transportation because of its Options:
  A) ligjtness
  B) low density
  C) high density
  D) high compressibility
  Show Answer
  The correct answer is D .
• Question 167: Which of the following metals will displace iron from a solution of iron(ll)tetraoxosulphate(lV)? Options:
  A) Copper
  B) Mercury
  C) Silver
  D) Zinc
  E) Gold
  Show Answer
  The correct answer is D .
• Question 168: Which of the following decrease when a given mass of gas is compressed to half its initial volume? Options:
  A) Atomic radius of each
  B) Average intermolecular distance
  C) Frequency of collisions
  D) Number of molecules presents
  Show Answer
  The correct answer is B .
• Question 169: When carbondioxide is bubbled into limewater a white precipitate is formed. If the passage of the gas is continued, the precipitate disappears. The reason for this is Options:
  A) calcium carbonate is formed which on reaction dissolves
  B) calcium hydrogen carbonate is precipitated and then dissolves
  C) calcium carbonate is formed which on reaction with further carbondioxide forms solube calcium hydrogen carbonate
  D) concentration of the solution has occurred with the deposition of calcium hydroxide
  E) the solution has become saturated and solid carbondioxide has been deposited
  Show Answer
  The correct answer is C .
• Question 170:

  NH_3(g) + HCl_(g) → NH₄Cl_(s)

  The entropy change in the system above is

  Options:
  A) negative
  B) indeterminate
  C) positive
  D) zero
  Show Answer
  The correct answer is A .