At 90 °C, a solution of 80 g of KNO3 in 100 g of H2O. How much KNO3 will precipitate out if the temperature is lowered to 10 °C?
80 g of KNO3
70 g of KNO3
40 g of KNO3
10 g of KNO3
70 g of KNO3
The solubility of KNO3 in water decreases as the temperature decreases. At 90 °C, the solution is saturated with 80 g of KNO3. As the temperature is lowered to 10 °C, the solubility of KNO3 decreases, causing some of it to precipitate out of the solution. Since the original solution contained 80 g of KNO3, at 10 °C, 70 g of KNO3 will remain dissolved in the water, and the remaining 10 g will precipitate out.