mole fraction (LiF)=
= (number of mole LiF)/(number of mole LiF + number of mole H2O)
In 100 g solution there are 39.4 g LiF and 100-39.4 = 60.6 g H2O.
1.
M(LiF) = 6.94 +19.00 = 25.94 g/mol
39.4 g LiF*1mol LiF/25.94 g LiF = 1.519 mol LiF
2.
M(H2O) = 2*1.01 + 16.00 = 18.02 g/mol
60.6 g H2O*1 mol H2O/18.02 g H2O = 3.363 mol H2O
3.
mole fraction (LiF)=
= (1.519 mol LiF)/(1.519 LiF + 3.363 mol H2O) = 0.311
mole fraction (LiF)=0.311
