calculate the molalityof ethanol solution in which the mole fraction of water is 0.88
Answers
Mole fraction of water = 1–0.040 = 0.960
Density of solution = Total mass/Total volume.
Total mass = mass of ethanol + mass of water.
Mass of ethanol = density of ethanol*volume of ethanol.
Mass of water = density of water*volume of water.
Total volume = volume of ethanol + volume of water
Let us name those variables
Density of ethanol = d1
Density of water = d2
Volume of ethanol = v1
Volume of water = v2
Now,
From above explanation
Mass of ethanol = d1*v1
Mass of water = d2*v2
Total volume = v1+v2
Total mass = (d1*v1)+(d2*v2)
Density = {(d1*v1)+(d2*v2)}/(v1+v2)
=[{d1*v1/(v1+v2)}+{d2*v2/(v1+v2)}]
Mole fraction is same as volume fraction. So,
v1/(v1+v2) = 0.040 , d1 = 0.8
v2/(v1+v2) = 0.960 , d2 = 1
Density of solution = (0.8*0.040)+(0.960*1)
= 0.032 + 0.960 = 0.992 g/ml