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Answer 1 · 2016-10-02T13:12:46

Given

#V->"Volume of the gaseous solute"=4L#

#P->"Pressure of the gaseous solute"=748mm=748/760atm#

#T->"Pressure of the gaseous solute"=27^@C=300K#

#n->"Number of moles of the gaseous solute"=?#

#R->"Universal gas constant"=0.082LatmK^-1mol^-1#

By equation of state for ideal gas

#PV=nRT#

#=>n=(PV)/(RT)=(748/760xx4)/(0.082xx300)=0.16mol#

Mass of solvent (benzene)#=58g=0.058kg#

Molality of the solution

#="moles of solute"/"mass of solvent in kg"#

#=0.16/0.058=2.76m#

The depression of freezing point

#DeltaT_f="molality"xxK_f#

#=2.76xx5.12=14.13^@#