Concept explainers
Consider the following solutions:
0.010 m Na3PO4 in water
0.020 m CaBr2 in water
0.020 m KCl in water
0.020 m HF in water (HF is a weak acid.)
a. Assuming complete dissociation of the soluble salts, which solution(s) would have the same boiling point as 0.040 m C6H12O6 in water? C6H12O6 is a nonelectrolyte.
b. Which solution would have the highest vapor pressure at 28°C?
c. Which solution would have the largest freezing-point depression?
a)
Interpretation: Among the given set of solutions, the one with the same boiling point of Glucose, highest vapor pressure and largest freezing point depression has to be determined.
Concept Introduction:
Colligative properties of a substance include the depression in the freezing point, elevation of boiling-point and osmotic pressure. These are dependant only on the number present and not based on the solute particles present in an ideal solution.
The vapor pressure of solution can be calculated from Raoult’s law,
Where,
The freezing point depression can be calculated from the equation,
Where,
Answer to Problem 79E
Answer
Explanation of Solution
To identify the solution that has the same boiling point as
Assuming complete dissociation, the effective particle concentrations of solution are,
Slightly greater
Therefore,
b)
Interpretation: Among the given set of solutions, the one with the same boiling point of Glucose, highest vapor pressure and largest freezing point depression has to be determined.
Concept Introduction:
Colligative properties of a substance include the depression in the freezing point, elevation of boiling-point and osmotic pressure. These are dependant only on the number present and not based on the solute particles present in an ideal solution.
The vapor pressure of solution can be calculated from Raoult’s law,
Where,
The freezing point depression can be calculated from the equation,
Where,
Answer to Problem 79E
Answer
Explanation of Solution
To identify which solution has highest vapor pressure at
As the concentration of solute decreases, the vapor pressure of the solvent gets increases because the mole fraction gets increased.
Hence,
c)
Interpretation: Among the given set of solutions, the one with the same boiling point of Glucose, highest vapor pressure and largest freezing point depression has to be determined.
Concept Introduction:
Colligative properties of a substance include the depression in the freezing point, elevation of boiling-point and osmotic pressure. These are dependant only on the number present and not based on the solute particles present in an ideal solution.
The vapor pressure of solution can be calculated from Raoult’s law,
Where,
The freezing point depression can be calculated from the equation,
Where,
Answer to Problem 79E
Answer
Explanation of Solution
To identify which solution has largest freezing point depression.
The largest freezing point depression is seen in
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Chapter 10 Solutions
Chemistry: An Atoms First Approach
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