When 2.0g of a non-volatile solute was dissolved in 90 gm of benzene, the boiling point of benzene is raised by 0.88K. Which of the following may be the solute?
`K_(b)` for benzene `=2.53 K kg mol^(-1))`

Options

A. `CO(NH_(2))_(2)`
B. `C_(6)H_(12)O_(6)`
C. `NaCI`
D. None of these

Answer

A

Explanation

`Na^(+)Cl^(-)` an ionic solid is not soluble in benzene
`therefore Delta T_(b)=K_(b)xxm`
`m=(Delta T_(b))/(K_(b))=(0.88)/(2.53)=0.348`
`m = (wxx1000)/(MxxW)`
`0.348=(2xx1000)/(Mxx90)`
`(["W = mass of solvent, w = mass of solute"])/(M = (2xx1000)/(90xx0.348)=63.86)`
Molar mass of urea, `CO(NH_(2))_(2)`
`=12+16+(14+2)xx2`
`=28+32=60 gmol^(-1)`
`therefore` Solute is urea (A)