[aisha89]

10g of KNO3 was added to 20.0 mL of water.It was boiled and cooled down, the precipitation temperature was 38 Celsius.
How to calculate solubility of KNO3 in moles per liter from the above information provided?
Any help will be appreciated..thanks

[Borek]

How many moles of KNO₃? How many liters of solution? How is solubility defined?

[AWK]

For this calculation you need a final density of your solution or at least its volume.

From your data you can calculate molality of solution (moles of solute per kilogram of solvent). Very often solubility is defined as mass of solute per 100 grams of solvent - this is molality of solution multiplied by molecular mass of solute and divided by 10.
Of course, such defined solubility you can calculate directly from your data.