Question

An x molal solution of a compound in benzene has mole fraction of solute equal to 0.2. the value of x is

Answer 1

mol fraction of solute=0.2
hence mol fraction of benzene=1-0.2=0.8
it means that 0.8 mol of benzene contains 0.2 mol of solute.
.................⇒0.8*78g of benzene contains 0.2 moles of solute
⇒ 62.4g.................................0.2mol...............
⇒1g......................................(0.2/62.4)mol.......
hence 1000g of benzene would contain (1000/62.4)*0.2 mol of solute=3.2=molality of solute=x