Question

calculate the molefraction of 40% by mass NaCl sloution in water​

Answer 1

40 moles of water=40 x 18=720 g

Considering the density of water as 1 g/ ml, the volume of water is 720 ml.

Also on dissolving 10g NaCl, there will not be considerably change in the volume of the solution. So the in 720 ml.of the Solution,10 g of NaCi is present.

So weight NaCl, in 1000 ml.of Solution

= 1000/720 x 10=13.89 g.

So Molarity of NaCl= Weight in 1Liter/Mol.Wt.

=13.89/58.5= 0.2374 M.

No.of Moles of NaCl=10/58.5=0.1707

No.of moles of water=40.

Mole Fraction of NaCl

=Moles of water/Total moles

= 0.1709/40.1709 = 0.004255

Mole Fraction of water=

(1–0.004255)=0.995745