Final answer:
To make a solution with 42 g KCl in 100 g H2O at 40°C, dissolve KCl in heated water and determine if all solute dissolves for an unsaturated solution or if excess remains for a saturated solution. Solubility curves help predict the saturation state of a solution.
Step-by-step explanation:
To make a solution containing 42 g KCl dissolved in 100 g H2O at a temperature of 40°C, one needs to measure out the respective masses of potassium chloride (KCl) and water (H2O). The water should be heated to 40°C, and then the KCl should be gradually added while stirring to ensure it dissolves completely. If all the KCl dissolves and no solid remains, the result is an unsaturated solution. If some KCl remains undissolved, then it becomes a saturated solution at that temperature. The term that describes a solution where no more solute can dissolve at a given temperature is a saturated solution.
It is essential to check a solubility curve for KCl at 40°C to determine if the solution will be saturated or unsaturated. If more solute could still be dissolved at that temperature, the solution would be considered unsaturated. Solubility curves are a useful tool for predicting whether a solution will be saturated or unsaturated under specific conditions.