Chapter 5.5, Problem 77P

Osmotic pressure measurements can be used to determine the molecular weights of large molecules such as protein. For a solution of large molecule to qualify as “dilute,” its molar concentration must be very law and hence the osmotic pressure can be too small to measure accurately. For this reason, the usual procedure is to measure the osmotic pressure at a variety of concentrations, then extrapolate the results to the limit zero concentration. Here are some data,* for the protein hemoglobin dissolved in water at 3°C:

The quantity $△h$ is the equilibrium difference in fluid level between the solution and the pure solvent, as shown in Figure 5.39. From these measurements, determine the approximate molecular weight of hemoglobin (in grams per mole).