PLEASE SHOW ALL FORMULAS AND DETAILED WORK. THANKS. Part A Calculate the vapor p

Question

PLEASE SHOW ALL FORMULAS AND DETAILED WORK. THANKS.

Part A

Calculate the vapor pressure of water above a solution prepared by dissolving 28.0 g of glycerin (C3H8O3) in 145 g of water at 343 K. (The vapor pressure of water at 343 K is 233.7 torr.)

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Part B

Calculate the mass of ethylene glycol (C2H6O2) that must be added to 1.00 kg of ethanol (C2H5OH) to reduce its vapor pressure by 9.00 torr at 35C. The vapor pressure of pure ethanol at 35C is 1.00×102 torr.

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Explanation / Answer

part A

from raoultrs law

Po - ps/Po = i*Xb

vapor pressure of water P0 = 233.7 torr

vapor pressure of solution P = ?

vanthoff factor = i = 1

xb = molefraction of solute = nb/(na+nb)

No of mol of water (na) = 145/18 = 8 mol

No of mol of glycerin (nb) = 28/92 = 0.304 mol

(233.7 - x)/233.7 = 1*(0.304/8.304)

x = vapor pressure of water in solution P = 225.14 torr

part B

from raoultrs law

Po - ps/Po = i*Xb

vapor pressure of ethanol P0 = 100 torr

DP = 9 torr

vanthoff factor = i = 1

xb = molefraction of solute = nb/(na+nb)

No of mol of ethanol (na) = 1000/46 = 21.74 mol

No of mol of ethylene glycol (nb) = ? mol

9/100 = 1*(x/(21.74+x))

x = No of mol of ethylene glycol (nb) = 2.15 mol

mass of ethylene glycol (mb) = 2.15*62 = 133.33 grams

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