In my opinion, this question is very icky
The molar mass of the compound could easily be two, three, or even four times that of the value you calculated depending on the physical properties of the compound itself. Freezing point depression and boiling point elevation is tricky in this respect as these two physical phenomena depend on the total concentration of solutes in solution, not total number of moles of substances dissolved in solution (a subtle, but nonetheless important distinction). For example, 1 mole of NaCl in H
2O would dissolve to give not 1 but 2 moles of solute! (1 mole of Na
+ ions and 1 mole of Cl
- ions) This would thus depress the freezing point of the solution by twice the amount calculated if ionization were ignored. However, in your case Sis290025, I believe it would be safe to ignore these thoughts