Final answer:
A solution with an osmolality four times greater than that of plasma would theoretically have a freezing point depression of approximately -14.8°C. This calculation assumes complete dissociation and thus, the actual freezing point could be less depressed. None of the given answer choices accurately reflects this freezing point depression.
Step-by-step explanation:
A solution with an osmolality four times greater than plasma would freeze at a temperature lower than that of plasma. To determine the freezing point depression, we can use the fact that the normal freezing point of water is 0.0°C and that a 1.0 m aqueous solution of NaCl (which is approximately equivalent to the osmolality of plasma) has a freezing point depression of about 3.7°C, considering complete dissociation of the electrolyte. If the osmolality is four times greater, we expect the freezing point depression to be four times as large, which implies a freezing point depression of 14.8°C (4 x 3.7°C = 14.8°C).
However, the actual measured value might differ from the theoretical due to incomplete dissociation of ions, as observed for sodium chloride at higher concentrations. Thus, the answer must be consistent with the given information that the freezing point of plasma decreases by 2.0°C per osmol (which for NaCl yields 3.7°C for complete dissociation). Therefore, multiplying by four, the expected freezing point depression would be approximately -7.4°C (4 x -1.86°C), which means the freezing point is -7.4°C and none of the provided answer choices (A. -0.56°C, B. -1.12°C, C. -1.68°C, D. -2.24°C) are correct as presented.