When you are admitted to the hospital for surgery, you are very often administered intravenously a physiological saline solution (a solution of NaCl in water). Calculate the concentration of this solution knowing that the solution has to be isotonic with blood and knowing that the average osmotic pressure of blood is 7.7 atm at 25 oC. Solution Pi (osmotic pressure) = iMRT molarity M = Pi/iRT = 7.7 / 2x[0.082 x (273.15 +25)] = 0.16 M i = Hoff factor = 2 since NaCl dissociates as Na+ and Cl-..