Molality of aqueous solution of urea is 4.What will be the mole fraction ofH2O?
Molality units is moles of solute per kilogram solvent.
In this case, we have
m = 4 moles urea / 1000 g H2O
Note that water has molar mass of 18 g/mol.
Getting the moles of water, we need to divide the given mass by its molar mass:
1000 g H2O / 18 g/mol = 55.56 mol H2O
Since we have 4 moles of urea, the total number of moles is
55.56 mol H2O + 4 mol urea = 59.56 moles
Finally, the mole fraction of H2O is
55.56 / 59.56 = 0.933
hope this helps~ `u`