JAMB - Chemistry (1991 - No. 16)
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 ?
57.5
42.2
28.6
14.3
คำอธิบาย
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
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