Q. 293.6( 86 Votes )
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).
Mole Fraction of Ethanol = 0.040
Density of water = 1g/ml(given)
So, Mole fraction of water = 1- 0.04 = 0.96Let,total mole in the solution=1
So, Moles of Ethanol = 0.04 moles.
Therefore, mass of 0.04 moles of ethanol = 0.04 mole × 46 gm/mole = 1.86 gm.
Density of ethanol = 0.789 g/ml.
Now, moles of water= 1-0.04 = 0.96 moles.Mass of water in this solution = 0.96 mole × 18 gm/mol = 17.28 gm.
Volume of water = =17.28 ml = 0.017 L.
Molarity of Solution = ==2.043 mol/L.
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