Answer:
6.97 grams
Explanation:
T = m × Kf
m ( molality) = T/Kf
T = -15°C = -15+273 = 258 K
Kf = 1.86°C/m = 1.86°C/m × 1K/1°C = 1.86 K/m
Molality = 258/1.86 = 138.71 mol/kg
Mass of ethylene glycol = molality×mass of water in kilograms×molecular weight of ethylene glycol
1 mole of water = 22.4 L
1 L of water = 1/22.4 = 0.045 mol
Mass of water = 0.045 mol × 18g/mol = 0.81 g = 0.81/1000 = 8.1×10^-4 kg
Mass of ethylene glycol = 138.71×8.1×10^-4×62 = 6.97 grams
