I'm confused with this chemistry problem?

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Answer 1 · 2017-11-30T21:39:06

I believe you used the mole fraction of the solute as opposed to the mole fraction of the solvent. It's a common mistake.

#P_(sol n) = chi_i P_0#

where chi is the mole fraction of solvent and P naught is the pure solvent's vapor pressure.

#chi_(C_6H_6) = (32.8g * (mol)/(78g))/((32.8g * (mol)/(78g) + 19.5g * (mol)/(154g)) approx 0.769#

is the mole fraction of benzene in our solution.

Hence,

#P_(sol n) = 0.769 * 100.84t o rr approx 77.50t o rr#

is the vapor pressure of that solution given those data.