Osmotic pressure...

16. A newly discovered protein has been isolated from seeds of a tropical plant and needs to be characterized. A total of 0.137g of this protein was dissolved in enough water to produce 2.00mL of solution. At 31.68°C the osmotic pressure produced by the solution was 0.134atm. What is the molar mass of the protein? (20pts)

Osmotic pressure is calculated using the equation:
P_os = cRTi
Where:
P_os = osmotic pressure
c = concentration, usually in units of molarity, M
R = Universal gas constant, 0.08206 ^L.atm/_mol.K in this case
T = absolute temperature in K
i = van't Hoff factor, the number of solute particles per formula unit
For this problem, the osmotic pressure and temperature are given. We'll assume that this "protein" is a single molecule, so i = 1. Plugging in:
0.134atm = M(0.08206 ^L.atm/_mol.K)(304.73K)(1)
Solving for molarity, M = 0.005359 ^mol/_L
We have 2.00mL of solution, that's 0.00200L, so our sample must contain (0.005359 ^mol/_L)(0.00200L) = 1.0717x10^-5 mols of protein. We measured 0.137g of protein, so the molar mass must be:
0.137g / 1.0717x10^-5 mols = 12780 ^g/_mol