Question

A KCl solution containing 44 g of KCl per 100.0 g of water is cooled from 67 ∘C to 0 ∘C. What mass of KCl will precipitate?

Answer 1

For this you will actually need the solubility curve for KCl. Here's a sample:

Now with this, we know that at 67 °C we have 44 g of KCl.

According to the graph, near the 70 °C we almost are at 50 °C, so we can assume here that at 67 °C, we are at 44 g/100 g H2O.

If you cooled from 67 °C to 0°C the solubility goes down from 44 g to 30 g, so, how many grams will precipitate?:

44 - 30 = 14 g of KCl

Hope this helps