Neco 2020 Chemistry Question 8

A student is investigating the solubility of potassium nitrate (KNO₃) in water at different temperatures using the apparatus shown. The set‑up consists of a 250 mL beaker placed on a thermostatically controlled water bath, a thermometer, a stirring rod, a filter funnel with filter paper, and a 100 mL graduated cylinder. The student adds excess solid KNO₃ to 100 mL of distilled water in the beaker, heats the mixture to a chosen temperature, stirs until no more solid dissolves, then filters the solution into the graduated cylinder and records the volume of the saturated solution. The experiment is repeated at 20 °C, 40 °C, 60 °C and 80 °C and the masses of KNO₃ that dissolve are found to be 13.0 g, 22.5 g, 33.0 g and 45.0 g respectively.