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JAMB Chemistry 2021 Question 12

Question 12

Solubility and Solutions

During the addition of 9.8kg of solid potassium chlorate (KClO3) into 40cm3 of water, it was heated to dissolve all the solid. As the solution cooled crystals of potassium chlorate started forming at 66°C. Calculate the solubility of potassium chlorate at 66°C.

  1. A.24.5moles per dm3
  2. B.0.2moles per dm3
  3. C.10.0moles per dm3
  4. D.2.0moles per dm3
Show the answer and explanation

Answer: D (2.0moles per dm3)

Explanation

Taking the mass as 9.8 g: moles of KClO3 = 9.8/122.5 = 0.08 mol in 0.040 dm3, so solubility = 0.08/0.04 = 2.0 mol dm−3.