How much ethyl alcohol must be added to 1 litre of water so that the solution will freeze at– 14°C ? (Kf for water = 1.86°C/mol)

Question. How much ethyl alcohol must be added to 1 litre of water so that the solution will freeze at– 14°C ? (K_f for water = 1.86°C/mol)

(a) 7.5 mol
(b)8.5 mol
(c)9.5 mol
(d)10.5 mol

Answer: (a) 7.5 mol