Question

The mole fraction of a solute in a 100 molal aqueous solution is ______ × 10^-2. (Round off to the Nearest Integer).

[Given :Atomic masses : H : 1.0 u, O : 16.0 u]

Options

• 20

• 80

• 64

• 69

Answer 1

The mole fraction of a solute in a 100 molal aqueous solution is 64 × 10^-2.

Explanation:

Molality of an aqueous solution of a solute = 100 m

Let the mole fraction of solute be x_a

Molality = `("Mole fraction of solute" xx 1000)/("Mole fraction of solvent" xx "Mol. mass of solvent")`

Then, `(x_"a" xx 1000)/((1 - x_"a")xx18)` = 100 m

`=> x_"a" = 18/28 = 0.6428 = 64.28 xx 10^-2 = 64 xx 10^-2`