7. A solution containing 90grams of KNO3 per 100. grams of H2O at 50.°C is considered to be
(1) dilute and unsaturated
(2) dilute and supersaturated
(3) concentrated and unsaturated
(4) concentrated and supersaturated

(4) concentrated and supersaturated

Explanation:

At 50.°C, 90g of KNO3 lies above the solubility curve [on the Regents Reference Table G]. This indicates that the solution is supersaturated, meaning it contains more solute than will naturally dissolve, and was formed when a saturated solution cooled. Furthermore, the percent concentration of this solution is 90% KNO3 making this solution concentrated. This can be calculated using the formula for mass percent concentration.

Percent Mass = Mass of Solute (g) x 100

                         Mass of Solution (g)

it's filtration, but this is an assumption so my apologies if i got this

the answer is a and have a great day