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JAMB Chemistry 1980 Question 15

Question 15

Mole Concept and Stoichiometry

5.00 g of hydrated salt of barium when heated to a constant weight gave 4.26 g of anhydrous salt with a molecular weight of 208. The number of molecules of water of crystallization in the hydrated salt is

  1. A.10
  2. B.7
  3. C.5
  4. D.2
  5. E.1
Show the answer and explanation

Answer: D (2)

Explanation

Water lost = 5.00 − 4.26 = 0.74 g = 0.041 mol. Anhydrous salt = 4.26/208 = 0.0205 mol. Ratio 0.041/0.0205 = 2 (BaCl2.2H2O).