How much potassium nitrate can be dissolved in 100 grams of water at 30°C?

In this case, you can estimate that the solubility of potassium nitrate in water at  

60

∘

C

is equal to about

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

.