Missing question: How many grams of silver would have to be dissolved in 1120 g of ethanol to lower the freezing point by 0.25ºC?Answer is: 15.18 grams of silver would have to be dissolved.
Kf(ethanol) = 1.99°C/m.
ΔT = Kf(ethanol) · b(solution).
0.25°C = 1.99°C/m · b(solution).b(solution) = 0.126 m.
m(ethanol) = 1120 g ÷ 1000 g/kg = 1.12 kg.
n(Ag) = m(ethanol) · b(solution).
n(Ag) = 0.126 m · 1.12 kg.
n(Ag) = 0.140 mol.
m(Ag) = n(Ag) · M(Ag).
m(Ag) = 0.140 mol · 107.87 g/mol.
m(Ag) = 15.18 g.