Question

If 80 grams CuSO4of a saturated solution at 80°Celcius is cooled down to 10°Celcius, how many grams of solute will be crystallized if the solubility by 80°C is 60 grams and at 10°C is 15 grams?

Answer 1

Answer:

solubility by 90°C is 80 grams and at 20°C is 30 grams

This statement needs elaboration.

For ease of calculation let us say:

solubility at 90°C is 80g solute in 100g solvent

Solubility at 20°C is 30g solute in 100g solvent

This unusual way of expressing solubility seems to be the standard method in texts which I have found dealing with solubility .

At 90°C : If you have 25g saturated solution, you have

Mass of solute = 25g / 180g * 80g = 11.11 g solute

At 20°C = You have the same 25g solution

Mass of solute = 25g / 130g * 30 = 5.77g solute

Mass of undissolved solute = 11.11g - 5.77g = 5.34g crystallises out.