Urea (NH2)2CO is dissolved in 100.0 g of water. The solution freezes at -0.085 degrees C. how many grams of urea were dissolved to make this solution.

Answer 1

delta T = K_f*molality
Plug in 0.085 for delta T, I assume you know K_f for water, calculate molality.
Then molality x kg solvent x molar mass = grams.
You have all but molar mass which can be calculated.