At 55.0 C, what is the vapor pressure of a solution prepared by dissolving 65.4
ID: 914315 • Letter: A
Question
At 55.0 C, what is the vapor pressure of a solution prepared by dissolving 65.4 g of LiF in 265 g of water? The vapor pressure of water at 55.0 C is 118 mmHg. Assume complete dissociation of the solute.
Submitted Answers
ANSWER 1: Deduction: -3%
42.7mmHg
ANSWER 2: Deduction: -3%
101mmHg
You have neglected the dissociation of LiF.
ANSWER 3:
100.741.mmHg
Use either an integer, decimal number, or scientific notation for the numeric portion of your answer. Do not use calculations or functions.
42.7mmHg
Explanation / Answer
Molar mass of water (H2O) = 18.015 gm/mol
Molar mass of Lithium Flouride (LiF) = 25.939 gm/mol
Number of moles of water = 265/18.015 = 14.71 moles
Number of moles of LiF = 65.4/25.939 = 2.521 * 2 (Li+ and F-) = 5.042 moles
Mole fraction of water = 14.71/(14.71+5.042) = 0.744
Pressure of Solution = molar fraction of H20 * pressure of H20
=> 0.7447 * 118 = 87.87 mm Hg
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