Acetic acid freezing point depression constant

A solution prepared by dissolving 3.00 g of ascorbic acid (vitamin C, C HsOg) in 50.0 g of acetic acid has a freezing point that is depressed by AT = 1.33°C below that of pure acetic acid. What is the value of the molal freezing-point-depression constant for acetic acid ... 

In principle, any of the colligative properties can be used to find the solute s molar mass, but in practice, some systems provide more precise data than others. For example, to determine the molar mass of an unknown solute by freezing point depression, you would select a solvent with as large a molal freezing point depression constant as possible (see Table 13.5). If the solute is soluble in acetic acid, for instance, aim concentration of it depresses the freezing point of acetic acid by 3.90°C, more than twice the change in water (1.86°C). 

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