Answer:
mole fraction of LiCl = 0.096
Explanation:
Weight percentage -
weight percentage of A is given as , the weight of the substance A by weight of the total solution multiplied by 100 .
i.e.
weight % A = weight of A / weight of solution * 100
GIven ,
20.0 wt% LiCl
Now ,
Assuming weight of solution = 100 g ,
weight if LiCl = 20.0 g
Since ,
Moles is denoted by given mass divided by the molecular mass ,
Hence ,
n = w / m
n = moles ,
w = given mass ,
m = molecular mass .
From the question ,
molar mass of LiCl = 42.39 g/mol
moles of LiCl = mass / molar mass = 20.0 g / 42.39 g/mol = 0.472 mol
Since , solution = 100 g ,
and ,
Solution = solute + solvent
100g = 20g + solvent
Solvent = 80 g
mass of water = 80 g
water molecular mass = 18 g/mol
moles of water = 80g / 18 g/mol = 4.44 mol
Mole fraction -
It is the ratio of the moles of one of the component of the solution by the mole of the solution .
Total moles of the solution = moles of the solute + moles of solvent
Total moles of the solution = 0.472 mol + 4.44 mol = 4.92 mol
Now ,
mole fraction of LiCl = moles of LiCl / total moles = 0.472 mol / 4.92
mole fraction of LiCl = 0.096
