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General Chemistry

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Chemistry of Solutions

Question
8 out of 10
 

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.

image\27303 Ch 8.jpg

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
Ans. B The observed changes in colligative properties are less than what was theoretically predicted. This is because the ionization of salts in water is not as complete as we expect. Some of the oppositely charged ions stick together and function as a unit. So the number of particles (units) is lower than what we expect. As the concentration increases, the possibility of the oppositely charged ions sticking together is greater than that in dilute solutions.

Chemistry of Solutions Flashcard List

10 flashcards
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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) The graph in the passage shows the solubilities of some compounds (salts). Which of the following is most likely true regarding the Compounds A, B, C and D?A The solubility process of Compound B is exothermic, and those of Compounds A, C and D are endothermicB The solubility process of Compound B is endothermic, and those of Compounds A, C and D are exothermicC The solubility processes of Compounds A, B, C and D are exothermicD The solubility processes of Compounds A, B, C and D are endothermic
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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 IIB The experimental values of the solution in Experiment II was more different from the theoretical calculations than the solution in Experiment IC Both experiments have the same extent of differences from the theoretical predictionsD The discrepancy noted in the experiments is absolutely a result of instrumental error, because the differences in Experiments I & II cannot change colligative properties
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