What is the mole fraction, x, of solute and the molality for an aqueous solution that is 16.0 % NaOH by mass

Step 1) identify the solvent and solute

solvent = H2O

solute = NaOH

Step 2) Assume that there are 100 grams total. Assume that the percent of the compound present is the number of grams present as well

100 g total

16g NaOH

84g H20

Step 3) convert grams to moles

84g H2O = 4.64 mol H2O

19 g NaOH = 0.400 mol NaOH

Step 4) mole fraction = moles A / (mol A + mol B + ...)

X = 0.400 / (0.400 + 4.64) = 0.079 (no units)

Step 5) convert g of solvent to kg

84 g H2O = 0.084 kg

Step 6) molality = moles of solute / kg of solvent

molality = 0.400 mol NaOH / 0.084 kg H2O

molality = 4.76 m