7:35 PM iPad F 65% digital.wwnorton.com Illinois State University CHE 140 001 SP

Question

7:35 PM iPad F 65% digital.wwnorton.com Illinois State University CHE 140 001 SP2017 General Ch... Smartwork5 sam@ilstu.edu 05/05/17 (1 This is a NumericEntry question/ltis worth 1 point/You have unlimited attempts/There is no attempt penalty See page 528 04 At 20.0°C, the vapor pressure of ethanol is 45 torr and the vapor pressure of methanol is 92 torr. 1st attempt lil see Periodic Table Q See Hint What is the vapor pressure at 20.00Cof a solution prepared by mixing 22.0 g of methanol and 77.0gof ethanol? torr 04/20 SUBM

Explanation / Answer

Ans 4 Lowering in vapor pressure is given as ,

Delta p = po x

where po is the vapor pressure of the pure solvent and x is the mole fraction of solute

number of moles of 22 g of methanol = 22/ 32 =0.6875

number of moles of 77 g of ethanol = 77 / 46 = 1.674

mole fraction of methanol = 0.6875 / (0.6875 + 1.674) = 0.29

Delta p = 45 x 0.29

Delta P = 13.1 torr

So the vapour pressure of solution = 45 torr - 13.1 torr = 31.9 torr

The vapour pressure of the solution is 31.9 torr

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