Answer:
a) Â 119 g/mol
Explanation:
-We apply the formula for freezing point depression to obtain the molality of the solution:
[tex]\bigtriangleup T_f=K_fm, \ \ K_f=1.36\textdegree C/m\\\\\therefore m=\frac{\bigtriangleup T_f}{K_f}\\\\=\frac{0.57\textdegree C}{1.36\textdegree C}\\\\=0.4191\ mol/Kg\\\\[/tex]
#We use the molality above to calculate the molar mass:
[tex]m=\frac{0.4191\ mol}{1\ Kg}=\frac{25\ g}{0.5\ Kg}\\\\\therefore 1 \ mol=\frac{25\ g}{0.5\ Kg}\times\frac{1\ Kg}{ 0.4191}\\\\=119.3033\approx 119\ g/mol[/tex]
Hence, the molar mass of the compound is 119 g/mol