Answer
$107.5\ g/mol$
Work Step by Step
Freezing point depression: $-0.36^{\circ}C$
Molality: $\Delta T_f=K_fm\rightarrow -0.36^{\circ}C=-1.86^{\circ}C/m\times m\rightarrow m=0.194\ mol/kg$
Molar mass: $0.52\ g\div(0.194\ mol/kg\times (25/1000)kg))=107.5\ g/mol$
