cms/mod/ibis/view.php?id 3320701 2/3/2017 12:00 PM 61.5l 100 1/29/2017 o9:00 PM
ID: 479326 • Letter: C
Question
cms/mod/ibis/view.php?id 3320701 2/3/2017 12:00 PM 61.5l 100 1/29/2017 o9:00 PM Grad Print H calculator Periodic Table estion 15 of 26 Incorrect Map Sapling Learning Biphenyl, C12Ho, is a nonvolatile, nonionizing solute that is soluble in benzene, CeHe At 25 C, the vapor pressure of pure benzene is 100.84 torr. What is the vapor pressure ofa solution made from dissolving 19.7 g of biphenyl in 34-2gof benzene? torr There is additional feedback available! View this feedback. bottom divider Click on the divider bar again to hide the additional feedback OPrevious view solution check Answer Next SExitExplanation / Answer
Since BP is non-volatile, it has negligible vapour pressure, so the only contribution to vapour pressure comes from benzene, which is volatile.
Raoult's Law states that the relative lowering of vapour pressure equals the mole fraction of solute in the solution.
BP has a RMM of 12*12+10*1=154 and benzene of 6*12+6*1=78, so 19.7 g of BP contains 19.7/154=0.127 mol and 34.2g of benzene contains 34.2/78=0.438 mol.
The mole fraction of solute is 0.127/(0.127+0.438 )=0.224, so the VP is lowered by0.224*100.84=22.58 torr.
The VP of the solution is 100.84-22.58=78.26 torr.
a)osmotic pressure=CRT
=>943*0.00131=C*0.0821*297
=>0.0506 M
b)moles=molarity*volume=0.0506*.315=0.0159
c)molecular weight=weight/no.of moles=3.39/0.0159=213.20 gms
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