Question

The above graph shows the solubility of benzoic acid in water at different temperatures. You are provided with 1.0 g of very impure benzoic acid which is dissolved in water at 90 °C. After hot filtration 0.2 g of the insoluble impurity was removed by hot filtration. The solution was allowed to cool ,crystallization occurred and pure benzoic acid was collected by filtration.

Calculate the maximum amount of benzoic acid that could be dissolved in 30 ml of water at90 °C.

Calculate the yield of recovered material if complete crystallization occurred at 30 C. Could this yield be improved? How What is the minimum amount of water that could be used in this exercise?

If the temperature dropped from 90 °C to 70 °C on hot filtration what is the maximum If the temperature dropped from 90 °C to 70 °C on hot filtration what is the maximum amount of benzoic acid that could be lost on the filter paper?

If 60 ml of water was used for the recrystallization, and the temperature dropped from 90 to 70 Con filtration calculate the minimum recovery of pure material on crystallisation at 30 °C.

Answer