試題詳解

40. Thyroxine, an important hormone that controls the rate of metabolism in the body, can be isolated from the thyroid gland. If 0.455 g of thyroxine is dissolved in 10.0 g of benzene, the freezing point of the solution is 5.144°C. Pure benzene freezes at 5.444°C and has a value for the molal freezing-point-depression constant of Kf of 5.12°C/m. What is the molar mass of thyroxine?
(A) 777,000 g/mol
(B) 777 g/mol
(C) 2330 g/mol
(D) 285 g/mol
(E) 3760 g/mol