Final answer:
A solution with 120 grams of NaNO₃ in 100 grams of water at 50 Celsius is supersaturated because it contains more solute than what can normally dissolve at that temperature.
Step-by-step explanation:
A solution of NaNO₃ that contains 120 grams of solute dissolved in 100 grams of H₂O at 50 Celsius can be best described as supersaturated. This is because at this temperature, the amount of NaNO₃ that can be dissolved in water exceeds the usual solubility limit, which means more solute is dissolved than what is capable of dissolving under normal circumstances. Should a seed crystal be introduced, or should the solution be perturbed, the excess solute is likely to precipitate out of the solution. This is indicative of a supersaturated solution, which is a metastable state that contains more solute than what the solvent would typically hold at a given temperature.
Supersaturation is achieved by dissolving additional solute at elevated temperatures and then allowing the solution to cool down slowly. If the cooling process is undisturbed, the solution can temporarily hold more solute than it would at equilibrium. Such solutions are prone to precipitation when a disturbance is introduced.