General chemistry question?
Hello guys, breezed through all my problems except this one. Now its driving me crazy
What mass of ethlene glycol, when mixed with 90.5 g H2O, will reduce the equilibrium vapor pressure of H2O from 1.00 atm to .500 atm at 100 C. The molar masses of water of water and ethylene glycol are 18.02 g/mol and 62.07 g/mol, respectively. Assume ideal behavior for the solution?
A. 90.5g
B. 156 g
C 181 g
D 263 g
E 312 g
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Verified answer
" Raoult’s law states that the vapor pressure of a component in a solution, PA =
the product of the mole fraction of the component (XA) and the vapor pressure of the pure component (PA°)"
PA = XA PA°
0.500 atm = mole fraction ( 1 atm)
mole fraction = 0.5
i.e half of the moles are glycol & half are water
use moar mass to find moles
90.5 g H2O @ 18.01 g/mol = 5.025 moles of water
find the mass of an equal number of moles of glycol:
5.025 moles of glycol @ 62.07 g/mol = 312 grams
your answer is
E 312 g
see:
http://virtual.yosemite.cc.ca.us/danielm/102/ppt/S...