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.)
Answer
15
Solution
Isotonic solutions have equal osmotic pressure, = iCRT.
NaCl dissociates completely (NaCl Na+ + Cl-), so i = 2 and
12 = 2 C 0.08 300
C = 1248 = 0.25 mol L-1
Molar mass of NaCl = 23 + 35.5 = 58.5 g mol-1
Strength = 0.25 58.5 = 14.625 g L-1 15 g L-1
Answer: 15