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JAMB Chemistry 1989 Question 19

Question 19

Mole Concept and Stoichiometry

A solution of calcium bromide contains 20 g dm−3. What is the molarity of the solution with respect to calcium bromide and bromide ions? [Ca = 40, Br = 80]

  1. A.0.1, 0.1
  2. B.0.1, 0.2
  3. C.0.1, 0.05
  4. D.0.05, 0.1
Show the answer and explanation

Answer: B (0.1, 0.2)

Explanation

CaBr2 has M = 200, so 20 g dm−3 is 0.1 M. Each formula unit gives 2 Br− ions, so [Br−] = 0.2 M.