# Addition of 0.40 g of a compound to 45.5 m L of benzene (density $0.879 g mL^{−1}$) lowers the freezing point from 5.51$^{\large\circ}$C to 4.998$^{\large\circ}$C. If $K_f$ for benzene is 5.12 K $Kg mol^{−1}$, calculate the molar mass of the compound.

400
Hence (A) is the correct answer.