Pure cyclohexane has a freezing point of 6.53 degrees Celsius. Its freezing poin

Question

Pure cyclohexane has a freezing point of 6.53 degrees Celsius. Its freezing point depression constant is: Kf= 20.0 degree Celsius m-1. A solution was made by taking 18.55g of an unknown nonelectrolyte and dissolving it in 150.0g of cyclohexane. The measured freezing point of the solution was -4.28 Celsius. Calculate the molecular weight of the unknown substance. Please show all your work

Explanation / Answer

depression in freezing point = 10.81 = Kf * molality molality = (18.55 / M) / 0.15 => 10.81 = 20 * (18.55 / M) / 0.15 => M = 228.8 Change in Temperature is the same in Kelvin or Celsius. So the unit has no effect in the answer

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