Question

Calculate molality of ethanol in H2O in which mole fraction of ethanol is 0.040.?

Answer 1

Mole fraction of ethanol is given that is 0.040 (X)

As in this case ethanol acted as solute

X= n2(ethanol)/n2(ethanol)+n1(no.of moles of water)

As the solution is diluted tus  

1lt of soln=1lt of water

n1(number of moles of water)= 1000g/18=55.5

By putting this in formula

0.040=n2(ethanol)/n2+55.5

By taking reciprocal of this

25=1+55.5/n2

25-1=55.5/n2

24=55.5/n2

n2=2.31

Thus, in 1000g of water contains 2.31 moles of ethanol

Therefore,the molarity of solution is 2.31M.