From the calculations and the information provided, the molar mass of the substance is 381 g/Mol.
The freezing point of a substance is the temperature at which the liquid is converted to solid.
Thus;
ΔT= K m i
K = freezing constant
m = molality
i = Van't Hoff factor
Given that;
10.5 °C= 29.8 °C/m * m * 1
m = 10.5 °C/29.8 °C/m
m = 0.35 m
Now;
0.35 = 100/MM/0.75
0.35 =100/MM * 1/0.75
0.35 = 100/0.75MM
0.35 * 0.75MM = 100
MM = 100/ 0.35 * 0.75
MM = 381 g/Mol
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