Calculate the molarity of a solution of ethanol in water, in which the mole fraction of ethanol is 0.040 (assume the density of water to be one).

Explanation

Number of moles in 1 L of water = `1000/18 = 55.55`
Assuming the given solution to be dilute, we have in 1 L of solution,
Mole fraction of ethanol `=("No. of moles of ethanol")/("No. of moles of ethanol + No. of moles of water.)`
or `0.040 = ("No. of moles of ethanol")/("No. of moles of ethanol" + 55.55")`
`=(55.55 xx 0.040)/(1-0.040)= 2.314`
Thus, 2.314 moles of ethanol are present in 1 L solution. Hence, molarity of the given solution = 2.314 M.