Question

how to calculate mole percentage plz explain with example?

Answer 1

Mole percent is equal to the mole fraction for the component multiplied by 100 per cent.
So,
mole % a = χa × 100 %

In a solution, the sum of the mole percentages for each component = 100%.

For a solution containing two components, i.e. solute and solvent—
mole % solute + mole % solvent = 100 %
Let's consider the following question-
"What are the mole fraction and mole percent of sodium chloride and the mole fraction and mole percent of water in an aqueous solution containing 25.0 g water and 5.0 g sodium chloride?
Identify the components making up the solution."
Well, we have,
NaCl as the solute and H2O as the solvent.
We calculate the moles of each component.
nNaCl = 5.0 g NaCl × (1mol NaCl ÷ 58.44g NaCl)
= 0.086 mol NaCl
nH ₂ O = 25.0 g H2O × (1 mol H2O ÷ 18.02g H2O) = 1.38 mol H2O
Then, we calculate the mole fraction of each component.
nt = n 1 + n 2 = (1.38 + 0.086) mol = 1.46 mol
χ2 = n2÷nt = 0.086 mol ÷1.46 mol = 0.058
χ1 = n1÷nt = 1.38 mol ÷ 1.46 mol= 0.942
(N.B.— It can also be written as
χ1 = 1– χ 2 = 1– 0.058 = 0.942)
Then, we calculate the mole percent of each component.
Mole % 2 =
χ2 × 100 % = 0.058 × 100 %
= 5.8 mole %
Mole % 1 =
χ1 × 100 % = 0.942 × 100 %
= 94.2 mole %
[N.B.— It can also be written as
mole % 1 = 100 – mole % 2 = (100 – 5.8) % = 94.2 mole %]

I hope this will clarify your doubt.