posted by CC .
A solution is prepared by dissolving 15.0 g of NH3 in 250.g of water. The density of the resulting solution is 0.974 g/ml. The mole fraction of NH3 in the solution is?
moles NH3 = 15.0/molar mass NH3.
If you didn't make a typo, you don't need density of water since you are given grams.
moles H2O = grams/molar mass.
XNH3 = moles NH3/total moles.