Question

Calculate the molarity of a solution of ethanol in water in which the mole

fraction of ethanol is 0.040?

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Answer 1

Molarity of solution:

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.

I hope it helps you