Question

if mole fraction of ethanol in aqueos solution is 0.1 then molality of solution will be ​

Answer 1

Answer:

The mole fraction of ethanol is equal to the ratio of the number of moles of ethanol to the total number of moles present in the solution.

For dilute solutions, 1 L of water (or 1 L of solution) contains

18

1000

=55.55 moles of water.

Let n be the number of moles of ethanol. The mole fraction of ethanol is 0.040.

Hence, 0.040=

n+55.55

n

n=0.040n+2.222

n=

1−0.040

2.222

=2.31 moles.

The molarity of the solution is the ratio of the number of moles of solute present in 1 L of solution.

As 1 L of solution contains 2.31 moles of ethanol, the molarity of a solution is 2.31 M.

Answer 2

Answer: The molality of the solution is $6.17 m$.

Explanation:

Given: mole fraction of ethanol $xa$ = $0.1$

Here ethanol is solute and water is the solvent.

As mole fraction of solute and solvent is equal to 1

$xa + xb =1$;

$xb = 1 -xa$

mole fraction of water $xb$ = $1-0.1 = 0.9$

To calculate molality $m$ of solution,

$m = \frac{xa * 1000}{xb * M}$

where $xa$ is the mole fraction of solute, $xb$ is the mole fraction of solvent and M is the molecular mass of solvent.

Molecular weight of water = $18 g mol^{-1}$

Putting the values to calculate the molality;

$m = \frac{0.1 * 1000}{0.9 * 18} = 6.17 molal$

Therefore the molality of solution is $6.17 m$.

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