Calculate the mole fraction of benzene in a solution containing 30 % by mass of it in carbon tetrachloride.

Explanation

Let us start with 100 of the solution in which
Mass of benzene = 30 g
Mass of carbon tetrachloride = 70 g
Molar mas of benzene `(C_(6)H_(6))=6xx12+6xx1=78" g mol"^(-1)`
`n_(C_(6)H_(6))=((30g))/((78 " g mol"^(-1)))=0.385` mol
Molar mass of carbon tetrachloride `(C Cl_(4))=12+4 xx 35.5 = 154 "g mol"^(-1)`
`n_( C Cl_(4))=((70g))/((154"g mol"^(-1)))=0.454` mol
`x_(C_(6)H_(6))=(n_(C_(6)H_(6)))/(n_(C_(6)H_(6))+n_(C Cl_(4)))=((0.385" mol"))/((0.385" mol")+(0.454" mol"))=0.459`.