Answer to Question #91132 in Organic Chemistry for S

Question

If 25g of water saturated with KClO3 at 70°C is cooled to 30°C, how much of this salt will precipitate out?

Answer 1

According to the solubility curve, 100 g of water can hold up to 30 g of the KClO₃ in the soluted state at 70 °C. We have 25 g of water, so there will be 30g/4=7.5 grams of the KClO₃ in this solution. On the other hand, the solubility of the KClO₃ at 30 °C is 10g per 100g of water or 2.5g per 25 grams of water. We have 7.5 grams of the potassium chlorate in the solution, while water can hold only 2.5g of this salt at 30 degrees. That means that there will be 7.5g - 2.5g = 5g of precipitate formed during cooling.

Answer: there will be 5 grams of the precipitate.