In an aqueous ethanol solution the mole fraction of ethanol is $0.10$ . Taking the molar mass of water as $18 g mo l^{- 1}$ , calculate the molality of ethanol. Give the answer in mol/kg to two decimal places.

Numerical answer type, answer in mol/kg, tolerance 0.01.

Answer: 6.17 mol/kg

For 1 mol of solution, ethanol

= 0.10

mol and water

= 0.90

mol

= 0.90 \times 0.018 = 0.0162

kg. So

m = 0.10/0.0162 = 6.17

mol/kg.