The osmotic pressure of a living cell is 12 atm at 300 K. The strength of sodium chloride solution that is isotonic with the living cell at this temperature is \_\_\_\_ g L ^ -1 . (Nearest integer) Given : R =0.08 ~L ~atm ~K ^ -1 ~mol ^ -1 Assume complete dissociation of NaCl (Given : Molar mass of Na and Cl are 23 and 35.5 ~g ~mol ^ -1 respectively.)
A. A
For osmotic pressure, using the van 't Hoff equation: = iMRT. The living cell has osmotic pressure of 12 atm. For an isotonic NaCl solution, the osmotic pressures must be equal. For NaCl solution: = i M R T, where i = 2 (complete dissociation into Na⁺ and Cl⁻). 12 = 2 M 0.08 300 12 = 48M M = 0.25 mol/L Molar mass of NaCl = 23 + 35.5 = 58.5 g/mol. Concentration in g/L = 0.25 58.5 = 14.625 15 g/L
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