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JAMB Chemistry 1978 Question 43

Question 43

Solubility and Solutions

Consider the solubility curves of three salts X, Y and Z given in the diagram. If each solution of the salt contains 200 g, and is heated to 100°C, which solution or solutions will deposit more than 100 g of the solute when suddenly cooled to 0°C?

Diagram for this question
  1. A.X only
  2. B.Y only
  3. C.Z only
  4. D.X and Z
  5. E.Y and Z
Show the answer and explanation

Answer: E (Y and Z)

Explanation

At 0°C the solubility of Y is about 80 g and of Z about 35 g, so cooling 200 g drops out over 100 g of each. X still dissolves about 170 g at 0°C, so it deposits only about 30 g.