Pure ethylene dibromide freezes at 9.80 °C . A solution is made by dissolving 0.213 g ferrocene (molecular formula Fe(C₅H₅)₂, molar mass = 186.04 g/mol) in 10.0 g ethylene dibromide. The freezing-point depression constant, kf, for ethylene dibromide is 11.8 °C/molal . What is the freezing point of this solution?
Strategy

To find the freezing point, use Equation 12.5, but first you must calculate the molality of the solution, m. This requires converting the quantity of ferrocene to moles and expressing the quantity of solvent in kilograms. Substitute these quantities into Equation 12.5 and solve for ΔT; then subtract this temperature change from the normal freezing point of ethylene dibromide.

Equation 12.5

Transcribed Image Text:

AT = mkf