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]

विकल्प

• 20

• 80

• 64

• 69

Answer 1

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

Explanation:

Given:

Molality (m) = 100 molal

This means 100 moles of solute are present in 1 kg (1000 g) of water.

Step 1: Calculate moles of water

Molar mass of water:

H₂​O = 2(1) + 16 = 18g/mol

Moles of water:

`1000/8 = 55.56` mol

Step 2: Calculate the mole fraction of the solute

`X_"solute"​ = "moles of solute"/"total moles"`

= `100/(100 + 55.56)`

= `100/155.56`

= 0.6429

`X_"solute​" ≈ 0.64`

Expressing it as n × 10⁻²

0.64 = 64 × 10⁻²