Final answer:
To create a saturated solution, the solution needs to be cooled to a temperature where the solubility of ammonium chloride is equal to 60 grams. According to the solubility curve, the solution needs to be cooled to 65 degrees Celsius.
Step-by-step explanation:
When a solution is supersaturated, it contains more solute than can normally dissolve at a given temperature. In order to create a saturated solution, the solution needs to be cooled to a temperature where the solute is in equilibrium with the solvent. According to the provided information, 60 grams of ammonium chloride is dissolved in 100g of water at 85°C. To create a saturated solution, the solution needs to be cooled to a temperature where the solubility of ammonium chloride is equal to 60 grams. Looking at the solubility curve, we can see that at approximately 65 degrees Celsius, the solubility of ammonium chloride is 60 grams per 100 grams of water. Therefore, the answer is 65 degrees Celsius.