Question

A solution of LiCl in water is 20.0 wt% LiCl. What is the mole fraction of LiCl?0.09600.4720.1064.44

Answer 1

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