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 491:

  How many atoms are present in 6.0g of magnesium? [Mg = 24, N.A = 6.02 x 10 ${}^{23}$mol]

  Options:
  A) 1.20 x 10${}^{22}$
  B) 2.4 x 10${}^{22}$
  C) 1.51 x 10${}^{22}$
  D) 3.02 x 10${}^{22}$
  Show Answer
  The correct answer is C .
• Question 492: 8.0 g of an element X react with an excess of copper (ll) tetraoxosulphate (lV) solution to deposit 21.3 g of copper. The correct equation for the reaction is?(Cu = 64). Options:
  A) X_(s) + CuSO_4(aq) → Cu_(s) + XSO_4(aq)
  B) X_(s) + 2CuSO_4(aq) → 2Cu_(s) + X(SO₄)_2(aq)
  C) 2X_(s) + CuSO_4(aq) → Cu_(s) + X₂SO_4(aq)
  D) 2X_(s) + 3CuSO_4(aq) → 3Cu_(s) + X₂(SO₄)_3(aq)
  Show Answer
  The correct answer is A .
• Question 493:

  Burning magnesium ribbon in air removes which of the following

  (i) oxygen (ii) nitrogen (iii) argon and (iv) carbon(iv)oxide?

  Options:
  A) i and iv only
  B) i, ii, iii and iv only
  C) i only
  D) i and ii only
  Show Answer
  The correct answer is C .
• Question 494:

  At 27°C, 58.5g of sodium chloride is present in 250cm${}^3$ of a solution. The solubility of sodium chloride at this temperature is?

  (molar mass of sodium chloride = 111.0gmol${}^{-1}$)

  Options:
  A) 2.0 moldm${}^{-3}$
  B) 0.25 moldm${}^{-3}$
  C) 1.0 moldm${}^{-3}$
  D) 0.5 moldm${}^{-3}$
  Show Answer
  The correct answer is A .
• Question 495: Calcium tetraoxosulphate (VI) dissolves in water only sparingly to form a Options:
  A) solution
  B) suspension
  C) precipitate
  D) colloid
  Show Answer
  The correct answer is C .
• Question 496: Diamond cannot be used Options:
  A) In making bicycle chains
  B) As abrasives
  C) In cutting glass and metals
  D) As dies for drawing wires
  Show Answer
  The correct answer is A .
• Question 497: In an attempt to remove sugar from a breaker containing a quantity of sand and sugar, 2 M ammonium chloride solution was accidentally added instead of water. Which of the following method could be used to remove the ammonium chloride from the mixture? Options:
  A) Fractional distillation
  B) crystallization
  C) Filtration followed by evaporation
  D) Evaporation followed by sublimation
  E) Filtration followed by sublimation
  Show Answer
  The correct answer is D .
• Question 498: The relative atomic mass of a naturally occurring lithium consisting of 90%$\frac{7}{3}$Li and 10%$\frac{6}{3}$Li is Options:
  A) 6.2
  B) 6.8
  C) 7.1
  D) 6.9
  Show Answer
  The correct answer is D .
• Question 499: 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 500: A hydrated salt of formula MSO₄.xH₂ O CONTAINS 45.3% by mass of water of crystalisation. Calculate the value of x [M = 56, S = 32, O = 16, H = 1 ] Options:
  A) 3
  B) 5
  C) 7
  D) 10
  Show Answer
  The correct answer is C .