Question

The solubility of potassium nitrate is 13 g per 100. mL of water at 0 oC and 246 g per 100. mL of water at 100.oC. A quantity of 246 g of potassium nitrate is dissolved in 100. mL of water at 100. oC and the solution is cooled to 0 oC. What percentage by mass of the KNO3 crystallizes at 0oC?

Answer 1

94.7%

Step-by-step explanation:

The solubility is the maximum amount of solute that can be dissolved in 100 mL (or 100g ) of solvent. Let's consider we have 100 mL of water

At 100 °C, 246 g of solute are dissolved. However, when the solution is cooled to 0 °C, only 13 g of KNO₃ remain dissolved. The mass that crystallizes is:

246 g - 13 g = 233 g

The percentage by mass of the KNO₃ that crystallizes is:

`(233g)/(246g) * 100\% = 94.7\%`