A very small amount of a non-volatile solute (that does not dissociate) is dissolved in `56.8 cm^(3)` of benzene (density `0.889 g cm^(3))`. At room temperature, vapour pressure of this solution is `98.88 mm Hg` while that of benzene is `100 mm Hg` . Find the molality of this solution. If the freezing temperature of this solution is `0.73` degree lower than that of benzene, what is the value of molal the freezing point depression constant of benzene?

Explanation

`(Deltap)/p_0=X_A=(100-98.8)/100=X_A=X_A=0.012`
`"Molarity"=(X_Axx1000)/((1-X_A)m_B)=(0.012xx1000)/(0.0988xx78)=0.1557`
`DeltaT=K_fxx"Molarity"`
`0.73=K_fxx0.1557rArr" "K_f=4.688`