The average osmotic pressure of human blood is 7.8 bar at 37ºC. What is the concentration of an aqueous NaCl solution that could be used in the blood stream?

0.153mol/L

To determine the concentration of an aqueous NaCl solution that matches the average osmotic pressure of human blood (7.8 bar) at 37°C, we can use the formula for osmotic pressure:

π = i × C × R × T

Where:

• π = osmotic pressure (7.8 bar)
• i = van't Hoff factor (number of particles the solute dissociates into)
• C = molar concentration of the solution (mol/L)
• R = universal gas constant (0.0831 L·bar·K⁻¹·mol⁻¹)
• T = temperature in Kelvin (37°C + 273.15 = 310.15 K)

For NaCl, which dissociates into Na⁺ and Cl⁻ ions, the van't Hoff factor (i) is approximately 1.9, accounting for incomplete dissociation in physiological conditions. Substituting the known values into the equation:

7.8 = 1.9 × C × 0.0831 × 310.15

Solving for C:

C = 7.8 / (1.9 × 0.0831 × 310.15)

C ≈ 0.153 mol/L

Therefore, the concentration of an aqueous NaCl solution that could be used in the bloodstream to match the osmotic pressure of human blood is approximately 0.153 mol/L.