a) The saturated solubility level of KCl (aq) at 40°C is 35.7 g/100 mL of water.
b) No, the solution would not be saturated at 90°C. At this temperature, the solubility of KCl in water is higher than at 40°C. Therefore, more KCl can dissolve in 100 g of water at 90°C than at 40°C. To determine if the solution is saturated, we need to compare the amount of KCl that actually dissolved in the water to the maximum amount of KCl that can dissolve in the water at that temperature. If the amount of KCl that dissolved is less than the maximum amount, then the solution is unsaturated. If the amount of KCl that dissolved is equal to the maximum amount, then the solution is saturated. If the amount of KCl that dissolved is greater than the maximum amount, then the solution is supersaturated.
c) Two ways in which saturation can be achieved if only 40 g of KCl is added to 100 g of water at 90°C are:
i) Heating the solution to a higher temperature: As the temperature of the solution is increased, the solubility of KCl in water also increases. Therefore, by heating the solution to a higher temperature than 90°C, more KCl can be dissolved in the water until the solution becomes saturated.
ii) Allowing the solution to cool slowly: If the solutionis heated to a temperature higher than 90°C and then allowed to cool slowly, the solubility of KCl in water decreases as the temperature decreases. This means that as the solution cools, KCl will begin to precipitate out of the solution until the solution becomes saturated. Alternatively, if the solution is left undisturbed at 90°C and allowed to cool slowly, KCl will begin to precipitate out of the solution as it reaches its saturation point.