The solubility of copper (II) tetraoxosulphate (Iv) is 75g in 100g of water at 100°C...

JAMB 1991

The solubility of copper (II) tetraoxosulphate (Iv) is 75g in 100g of water at 100°C and 25g in 100g of water at 30°C. What mass of the salt would crystallize, if 50g of copper (II) tetraoxosulphate (VI) solution saturated at 100°C were cooled to 30°C ?

A. 57.5
B. 42.2
C. 28.6
D. 14.3

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Correct Answer: Option D

Explanation

solute + solvent = solution

at 100oC; 75g + 100g = 175g

at30oC; \(\frac{25g}{50g}\) + 100g = 125g

From 100oC - 30oC; 175g CuSO4 ppt 50g

From 100oC - 30oC; 50g CuSO4 ppt \(\frac{50 \times 50}{175}\) = 14.3

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