Question

Predict the mole fraction of b in the vapor produced when a mixture of 0.70 mole fraction of a and 0.30 mole fraction of b boils.

Answer 1

Mole  fraction  of  a  component  in a solution is  the  ratio  of  the  number   of  moles  of  that  component  to  the  total  number  of  moles  of  all   component  in  a   solution.
total  moles =0.30  +0.70=1.00
mole  fraction  of  b={(0.30  x100)/(1  x100 )}=3/10