Question

Calculate the molarity and molality of 20% aqua solution ethanol solution by mass/ volume. Density of solution is equals to 4.96 gram ml

Answer 1

20% aqueous ethanol solution by volume means 20 ml/ ethanol in 80 ml/ water.

Density of the solution as 0.960 g/cm3 or 0.960 g/ml

Now,

Mass of solution = density x volume

= 0.960 x 100

= 96 g

Mass of 80 ml water = density of water x volume of water

= 1g/ml x 80 ml = 80 g

Mass of ethanol in solution = mass of solution - mass of water

= 96-80 = 16 g

Molar mass of ethanol,(C2H5OH) = 12 x 2 + 5x 1 + 16 + 1

= 46 g

Number of moles of ethanol = 16/46 = 0.348

Molarity = number of moles/volume in litres

= 0.348/0.1

= 3.48 M

Molality = number of moles of solute/ mass of solvent in Kg

= 0.348/0.08

= 4.35 m

Answer 2

Answer:

Explanation:M=x*d*10/M

M=20*4.96*10/46

M=992/46

M=21.56

m=x*1000/M*(100-x)

m=20*1000/46*(100-20)

m=2000/46*80

m=5.43

x=%of solution

d=density

M=molecular weight of ethanol