1- An organic chemist has an impure solid (X) which is soluble in water to the extent of 3 g per 100 ml of water at room temperature and 15 g per 100 ml of water at 100 °C. 10 g of X has 1 g of impurity A (A has the same solubility in water as X) and 0.40 g of impurity B (B is insoluble in water). How could you purify X? How many grams of pure X could be obtained after one recrystallization from water?
For recrystallization from water we need to take 34 ml of water, then 1 g of water-soluble impurities will dissolve, but also will dissolve and substance X (1 g). Then the substance should be washed with isopropanol and hexane, may insoluble impurities dissolve in solvents affine! At the end turn out about 7.5 g of pure substance X.