Question

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).

Answer 1

Mole fraction of C 2H 5OH= 0.040 mol (given)

Let the moles of C 2H 5OH in solution be = x

Mole fraction of C 2H 5OH = number of moles of C 2H 5OH/ number of moles of solution….(eq.1)

Density of water = 1 (given)

And the weight of 1000ml of water = volume X density (formula for density = mass/volume)

                                                       = 1000 x 1=1000g

Therefore moles of water = 1000/18 (18g is molecular mass of water)

                                          = 55.55  mol  

Putting the values in equation 1,

We get

               

         

                                 x  = 2.3145 mol  

Molarity of solution = 2.314 M