Concept explainers
The density of an aqueous solution containing 15.0 percent of ethanol
Interpretation: The molarity, molality, and volume of the given solutions are to be calculated.
Concept Introduction:
Molarity
Its expression is
Molality
The expression to calculate moles is
Answer to Problem 24QP
Solution:
(a)
(b)
(c)
Explanation of Solution
Given information:
Density of the solution is
Percent by mass of ethanol is
Moles of ethanol is
Explanation:
a) The molality of the solution
The mass of ethanol is
Mass of solution = mass of solvent + mass of solute.
Substitute
The expression to calculate moles is
Ethanol has a molar mass of
Substitute
The expression to calculate molality is
The mass of solvent is in grams and can be converted into kilograms by the following relation:
Thus, the conversion factor used to convert volume from milliliters into liters is
Convert
Substitute
Therefore, the molality of the solution is
Explanation:
b) Molarity of solutions
Density of the solution is
Therefore, the conversion factor becomes
Multiply the conversion factor with
The volume of solvent is in
Thus, the conversion factor used to convert volume from milliliters into liters is
Convert
The expression to calculate molarity is
Substitute
Therefore, the molarity of the solution is
Explanation:
c) The volume of the solution that would contain 0.250 mol of ethanol.
Since, molarity is the number of moles of solute dissolved in
Invert the conversion factor and multiply it with moles of ethanol in order to calculate the volume of solution as:
Therefore, the volume of the solution is
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Chapter 13 Solutions
Chemistry
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