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)
Two experiments were conducted for analyzing the solubility properties and their effects on colligative properties. In Experiment I, a 1.0 m solution of KBr was analyzed and in Experiment II, a 2.3 m solution of KBr was analyzed. The experimental values of freezing and boiling points were slightly different from the expected values based on the theoretical calculations discussed in the passage. Which of the following is most likely correct regarding the two experiments?
|A||The experimental values of the solution in Experiment I was more different from the theoretical calculations than the solution in Experiment II|
|B||The experimental values of the solution in Experiment II was more different from the theoretical calculations than the solution in Experiment I|
|C||Both experiments have the same extent of differences from the theoretical predictions|
|D|| The discrepancy noted in the experiments is absolutely a result of instrumental error, because the differences in Experiments I & II cannot change colligative properties|