Question

The solubility of compound A in ethanol is 0.5 g per 100 mL at 0oC and 5.0 g per 100 mL at 78oC.

(a)
To make a hot, saturated solution of 15.0 g of A at 78oC, how much ethanol is required?

(b)
When the solution prepared in is cooled to 0oC, how much of compound A will be crystallized? How much of A would remain in solution and would not be recoverable?

Answer 1

a.
100 mL x 15 g/5.0 g = 300 mL ethanol required to prepare a saturated solution.

b. After cooling this to 0C,
0.5 g x (300 mL/100 mL) = 1.5 g that will be lost due to solubility.
Amount recovered will be 15.0-1.5 = ? recrystallized.