A certain salt is known to have a solubility in water of 25.2g/100g water at 100°C and 11.4g/100g water at 20°C. The salt is dissolved in 240 g of water at 100°C until no more solid will dissolve. How much salt will crystallize out when the solution is cooled to 20°C?

Answer 1

How much will dissolve in 240 g H2O at 100 C? That will be
25.2 x (240/100) = ?

How much will dissolve when cooled? That will be
11.4 x 240/100 = ? g in solution.
Then grams at 100 (from above calcn) - g in soln at 20 = grams that will crystallize.