Question

A solution of 12.00 grams of an unknown nonelectrolyte compound is dissolved in 200.0 grams of benzene. The resultant solution freezes at 3.45^oC. What is the molar mass of the unknown compound? [The freezing point of pure benzene is 5.45^oC ; the K_f for benzene is 5.07^oC m^-1]. (Hint: this is a two-step challenge, involving first finding the number of moles of solute in the solution from the freezing point data and then its molar mass in units of grams/mole)

A. 125 grams per mole

B. 152 grams per mole

C. 88.2 grams per mole

D. 55.8 grams per mole

E. 193 grams per mole