16 g NaOH has 84 g of water moles of NaOH =16/40 =0.4 moles of water =84/18 = 4.667 Total moles = 0.4+4.667 = 5.067 mole fraction of NaOH = 0.4/5.067 = 0.0789 Conclusion: 84 g water will have 0.4 moles of NaOH 1000g water will have [0.4x 1000]/84 = 4.76 moles This is called molality. ENJOY :)