Answer:
[tex]m_{cryst}=58g[/tex]
Explanation:
Hello there!
In this case, according to the attached solubility chart, it is possible for us to realize that about 88 grams of KNO3 are soluble at 50 °C but just 30 grams are soluble at 20 °C in the same 100 g of water.
In such a way, the crystalized mass of this solute can be calculated by subtracting the mass at 50 °C and the mass at 20 °C:
[tex]m_{cryst}=88g-30g\\\\m_{cryst}=58g[/tex]
Best regards!