What is the molar mass of a covalent compound if 0.486 g of it is dissolved in 25.0 ml of water and produces a freezing temperature of - 0.40 °c?

Answer is: the molar mass of a covalent compound is 90.4 g/mol.

m (compound) = 0.486 g.

m (water) = 25 mL · 1 g/mL = 25 g : 1000 g/kg = 0.025 kg.

ΔT = 0°C - (-0.40°C) = 0.40°C.

Kf (H₂O) = 1.86°C/m.

M (compound) = Kf · m (compound) / m (water) · ΔT.

M (compound) = 1.86°C/m · 0.486 g / (0.025 kg · 0.4°C).

M (compound) = 90.4 g/mol.