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JAMB Chemistry 1997 Question 16

Question 16

Mole Concept and Stoichiometry

On recrystallization, 20 g of magnesium tetraoxosulphate (IV) forms 41 g of magnesium tetraoxosulphate (IV) crystals, MgSO4.yH2O. The value of y is [Mg = 24, S = 32, O = 16, H = 1]

  1. A.1
  2. B.3
  3. C.5
  4. D.7
Show the answer and explanation

Answer: D (7)

Explanation

Water taken up = 41 − 20 = 21 g = 21/18 ≈ 1.17 mol. MgSO4 = 20/120 ≈ 0.167 mol. y = 1.17/0.167 = 7.