How much potassium nitrate do you think could dissolve in 100 mL of water at 60°C?

Your tool of choice here will be the solubility graph for potassium nitrate, #"KNO"_3#, in water.

The solubility graph is a very useful tool because it tells you the amount of potassium nitrate that can be dissolved per #"100 mL"# 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 #60^@"C"#, start from the #60^@"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 #60^@"C"# is equal to about

#color(darkgreen)(ul(color(black)("solubility " ~~ " 110 g / 100 mL water")))#

This tells you that a saturated solution of potassium nitrate will hold about #"110 g"# of dissolved salt, i.e. of dissociated salt, per #"100 mL"# of water at #60^@"C"#.