Answer
see solution
Work Step by Step
The solubility of $KNO_3$ in water is 316 g/L at 20 'C.
It is given in the problem that 28 g of $KNO_3$ is dissolved in 100 g of water, so:
For water, 1 mL = 1 g. So, 100 mL = 100 g
Then, the solubility of $KNO_3$ = 31.6 g / 100 mL.
The given solution contains only 28 g of $KNO_3$. SO, it can still dissolve additional amounts of KNO3. Hence it is an unsaturated solution.
