Chemistry of Solutions
The concentration of solutions are generally expressed in terms of molarity, molality, normality, and weight percent. The formation of the solutions itself has many ramifications. The solubility of solutes differ considerably from one other. Some of the factors that can influence the solubility include temperature and pressure. Solubility depends on other factors as well. Given below in Figure-1 is a graph which depicts solubility differences of some solutes.
Quite often, the freezing and boiling point changes that are brought about by the dissolved solutes can be predicted reasonably. But this is not always the case.
The predictions and calculations are done for freezing point depression (ΔTf) based on the following formula:
ΔTf = Kf m,
where m is the molality and Kf is the freezing point depression constant. (Kf= 1.86 oC/m)
For boiling point elevation (ΔTb), the calculations are based on the following formula:
ΔTb = Kb m,
where m is the molality and Kb is the boiling point elevation constant. (Kb = 0.512 oC/m)
A solution was made by using 315 g of glucose in 750 g of water. What is the boiling point of this solution?
|D|| 101.20 C|
ΔTb = Kb m = (0.5120 C/m)(2.33 m) = 1.20 C.
The answer is 1000 C + 1.20 C = 101.20 C.