Question

The solubility of acetanilide in hot water (5.5g/100ml at 100℃) is not very great, and its solubility in cold water (.53g/100ml at 0℃) is still significant. What is the maximum theoretical percent recovery from the crystallization of 5g of acetanilide from 100ml of water (assuming the solution is chilled to 0℃ for filtration).

Answer 1

At 100 C, 50 mL of water will dissolve 2.75 g of acetanilide (since 100 mL will dissolve 5.5 g).

Thus, all of the 2.5 g sample will be dissolved in the 50 mL of water.

Upon cooling, the solubility decreases to 0.265 g/50 mL.

This is the maximum amount that can be retained in 50 mL solution. The remaining 2.50 - 0.265 = 2.235 g crystallizes from solution.

This gives a % recovery of (2.235/2.50) * 100% = 89.4%