Answer: 62 gram
Step-by-step explanation:
Using attached solubility graph
This solubility graph tells us the amount of potassium nitrate that can be dissolved per 100g of water in order to have a saturated solution of potassium nitrate at a given temperature.
In order to find the solubility of the salt at 40∘C, start from the 40∘C mark on the graph and move up until you intersect the curve. At the point of intersection, move left until you intersect the y axis and read off the value that you land on.
In this case, you can estimate that the solubility of potassium nitrate in water at 40∘C is equal to about 62g
This tells you that a saturated solution of potassium nitrate will hold about 62 g of dissolved salt, i.e. of dissociated salt, per 100g of water at 40∘C.
Please find the attached file for the graph.