Exercise 1 | Colligative Properties of Solutions

Molality m (in mol.kg^-1):
 

m = $\frac{{\mathrm{n}}_{\mathrm{solute}}}{{\mathrm{m}}_{\mathrm{solution}}}$

n_solute = m_solute / M_solute = m_solute / (6 M_C + 12 M_H + 6 M_O)

n_solute = 23.0 / 180.12 = 1.28 x 10^-1 mol

m_solution = V_solution x d (with d = density of water = 1.00) = 0.500 kg

m = $\frac{1.28 \times {10}^{-1}}{0.5}$ = 2.55 x 10^-1 mol.kg^-1

Mole Fraction:
 

x_solute = $\frac{{\mathrm{n}}_{\mathrm{solute}}}{{\mathrm{n}}_{\mathrm{solution}}}$

n_solute = 23.0 / 180.12 = 1.28 x 10^-1 mol

n_solution = 500 / 18.0 = 2.78 x 10¹ mol
 

x_solute = $\frac{1.28 \times {10}^{-1}}{27.8}$ = 4.60 x 10^-3