Chemistry 2 chapter 13 question

Question

A solution of NaCl in water has molality of 1.55. What is a mole fraction Xnacl.

Answer 1

A molality of 1.55 m means there are 1.55 moles of NaCl in 1 kg of H2O

Mole fraction of NaCl is moles of NaCl / total moles of solution

moles NaCl = 1.55 mols

moles H2O = 1 kg H2O = 1000 g H2O x 1 mol H2O / 18 g = 55.6 mols H2O

Total moles = 1.55 + 55.6 = 57.15 moles

X_NaCl = 1.55 / 57.15 = 0.0271