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 291:

  

  From the diagram above, find the amount of solute deposited when 200 cm³ of the solution is cooled from 55^oC to 40^oC

  Options:
  A) 0.10 mole
  B) 0.20mole
  C) 0.01 mole
  D) 0.02 mole
  Show Answer
  The correct answer is B .
• Question 292: A metal is extracted from its ore by the electrolysis of its molten chloride and it displaces lead from lead (ll) trioxonitrate (V) solution. The metal is Options:
  A) copper
  B) aluminium
  C) zinc
  D) sodium
  Show Answer
  The correct answer is D .
• Question 293: 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 294: An oxidation state of or in K2CrO7 Options:
  A) 7
  B) 6
  C) 5
  D) 4
  Show Answer
  The correct answer is B .
• Question 295: Which of the following reactions is correct as as written? Options:
  A) FeCl₂ + 3NH₄OH → Fe(OH)₃ + 3NH₄Cl
  B) Pb₂O₃ + 4HCl → PbCl₂ + 2H₂O
  C) PbNO₃ + H₂S → PbS + 2HNO₃
  D) NaOH + H₂SO₄ → NaHSO₄ +H₂O
  E) 2NH₄NO₃ → N₂ + 2H₂O
  Show Answer
  The correct answer is D .
• Question 296: Water for town supply is chlorinate to make it free from Options:
  A) bad colour
  B) bacteria
  C) temporary hardness
  D) permanent hardness
  Show Answer
  The correct answer is B .
• Question 297:

  CU₂S_(s) + O_2(g) → 2CU_(s) + SO_2(g)

  What is the change in the oxidation number of copper in the reaction above?

  Options:
  A) +1 to 0
  B) 0 to +2
  C) +2 to +1
  D) 0 to +1
  Show Answer
  The correct answer is A .
• Question 298: The radio active radiation used in studying the arrangement of particles in giant organic molecules is Options:
  A) $\gamma$- rays
  B) $\alpha$- particles
  C) X-rays
  D) $\beta$ - particles
  Show Answer
  The correct answer is C .
• Question 299: If the difference in electronegativity of elements P and Q is 3.0. The bond that will be formed between them is Options:
  A) metallic
  B) covalent
  C) co-ordinate
  D) ionic
  Show Answer
  The correct answer is D .
• Question 300:

  16.8 g of sodium hydrogen trioxocarbonate (IV) is completely decomposed by heat. Calculate the volume of carbon(IV) oxide given off s.t.p

  [Na 23, C = 12, O = 16, H = 1, Molar volume of a gas at s.t.p = 22.4 dm³]

  Options:
  A) 22.40 dm³
  B) 11.20 dm³
  C) 2.24 dm³
  D) 1.12 dm³
  Show Answer
  The correct answer is C .