Question

calculate the molality of a solution of ethanol in water in which the mole fraction of ethanol is 0.040.​

Answer 1

Answer:

Mole fraction of $C_{2}H_{5}OH$ = $\frac{No. of moles of  C_{2} H_{5}OH}{No. of moles of solution}$ ⇒ 1

Let the moles of $C_{2}H_{5}OH$= X

Now density of water = 1 (given)

And the weight of 1000ml of water = volume * density (from density = mass/volume)

= 1000 x 1=1000g

Therefore moles of water = $\frac{1000}{18}$ = 55.55 mol (18g is molecular mass of water)

Also mole fraction of $C_{2}H_{5}OH$= 0.040 (given)

Putting the values in equation 1 ,we get

= 0.040 = X/X+55.55

= 0.040X+2.222 = X

OR X = 2.3145 mol

Molarity of solution = 2.314 M