Question

Mole fraction of solvent in (aq) sol. Of NaOH having molality 3

Answer 1

Mole fraction = moles of solution /total moles of solution

Answer 2

If m = 3, it means 3 moles of NaOH will dissolve in 1000 gm. of H2O (water). So we take mass of solvent as 1000 gm.
Then, no. of moles of solvent (water) = 1000/ 18 (as mass of H2O is 18)
So our required mole fraction is (1000/18) / ( 1000/18 +3) = (1000/18) / ( 1054/18)
= 1000/ 1054 = 500 / 527 .
So our ans is 500/527