Question

Suppose we are dealing with calcium chloride as opposed to the chemical in the video. If a solution contains 70 g of calcium chloride per 100 g of water at 25 degrees Celsius, is the solution unsaturated, saturated, or supersaturated? Explain your answer. You may want to refer to Figure 13.4 in your text for help, or perhaps refer to the image at http://chemistrysolutions.files.wordpress.com/2011/03/capturada16.jpg..

Answer 1

@Butchy @iPwnBunnies

Answer 2

Looking up the literature for CaCl2, it is saturated at 74.5 g/100mL (20 °C). In the problem, the temperature is increased, and in general, as temperature increases, so does the solubility curve. Since in the problem 25 C is the temperature, the saturation point of 74.5 is going to be passed, thus the solution is supersaturated at 25 degrees C at the 70/100 g concentration. However, looking at a solubility curve, you can easily see that the curve for CaCl2 is above that of NaCl (which is the reference solute dissolved in 100 mg of H20). Anything above this line is supersaturated and below unsaturated. Therefore, since we have 70/100 gm water the solution is unsaturated.

Answer 3

Does that make sense?

Answer 4

Since the heat goes up so does the solubility which means 100 mL of water can dissolve more than 74.5 g of CaCl2 but since the solubility at 20°C is of 74.5 g per 100 mL, it's not supersaturated,
so yes I would say like you that it's unsatured since more CaCl2 can dissolve, and if you don't add more CaCl2 even if the solution cools down to 20°C CaCl2 won't precipit.