Question

Molality of an aqueous solution having mole fraction of solvent as 0.95 is approximately

Answer 1

Answer:- 2.94m

Solution:- Molality is moles of solute per kg of solvent. The given info says, the mole fraction of solvent as 0.95.

Since the solution is aqueous, the solute must be dissolved in water. It means the solvent is water. The sum of mole fractions is always 1. So, if the mole fraction of solvent is 0.95 then the mole fraction of solute = 1 - 0.95 = 0.05

If we assume total 1 mol of the solution then the solution would have 0.05 moles of solute and 0.95 moles of solvent and the calculations for the moles of solute and solvent could be shown as:

mole fraction of solute = $(\frac{solute mol}{solution mol})$

$0.05=(\frac{solute mol}{1})$

solute mol = 0.05(1) = 0.05

Similarly, solvent mol = 0.95(1) = 0.95

Molar mass of water is 18.02 gram per mol. Let's multiply the moles of solvent(water) by it's molar mass to convert moles to grams:

$0.95mol(\frac{18.02g}{1mol})$

= 17 g

Convert g to kg:

$17g(\frac{1kg}{1000g})$

= 0.017 kg

molality of the solution = $\frac{0.05mol}{0.017kg}$

molality = 2.94 m

So, the molality of the solution is 2.94m.

Answer 2

Molality: Molal concentration is the measurement of the degree of concentration of a solute in a solution. Molal concentration is also called molality.

Given:

• Aqueous solution
• Mole fraction = 0.95

Formula:

Molality =  Mass of solute / Molar mass solute.

The solution is aqueous and so, the sum of mole fractions is always 1.

If the mole fraction of solvent is 0.95 then,

Mole fraction of solute = 1 - 0.95 = 0.05

Moles of solute and solvent,

Mole fraction of solute = solutemol/solutionmol

Therefore,

Solute mol = 0.05

Solvent mol = 0.95

Molar mass of water is 18 gram per mole.

To convert moles to grams,

0.95(18/1) = 16.8 grams

To convert gram to kilogram,

16.8(1/1000) = 0.016 kg

Molality of the solution = 0.05/0.016

Therefore,

Molality ≅2.94 m