Question

if the mole fractio of NaCl in an aqueous solution is 0.0927, what is the wt/wt% (percent by mass) of NaCl

Answer 1

mole NaCl = 0.0927

mole H2O = 1.0000 - 0.0927 = 0.9073

then

mass NaCl = 0.0927mole x (0.9073g / mole) = 0.1022 g

mass H2O = 0.9073 mole x (18.02g / mole) = 16.35 g

and therefore;

mass % NaCl = [(0.1022g NaCl) / (58.45g NaCl + 18.016g H2O)] x 100% = 24.9%

=24.9%