[MilkyCar]

I've been doing a homework assignment and I've bumped into this problem, it reads:

a 0.14 g sample of a purified protein is dissolved in water to give 2.0 mL solution, the Osmotic pressure is found to be 12.2 torr at 25°C, calculate the protein's molar mass.

I did Pi/MRT which is 12.2 torr x ? = M x ? x 298K

I divided 12.2/760 since I wanted to convert it to atm, and I know that the Gas constant for R is 0.08206 L atm/mol K.

So I got (12.2/760)/0.08206 x 298 which came out to be 0.66 x 10^-3 mol/L.

I did 2.0 mL/1000 L to get 0.0020, and I used that for the second step.

To find the molarity of the protein, I did 0.0020L x 0.66 x 10^-3 mol protein/L and got 1.3 x 10^-6 mol protein.

I tried to find the molar mass on the third and final step by doing 0.14 g/1.3 x 10^-6 mol and got 10.8 x 10^4 g/mol

I think I got something incorrect in my calculations, and I need help with this

[Borek]

Don't use rounded down values in the calculations (use full accuracy or at least some so called "guard digits"), round down only the numbers you report.

Other than that looks OK.

[Babcock_Hall]

A single polypeptide is often in the range of 5000 to 260,000 in molecular weight, with some outliers.  Your answer is within this range, if that is what you were wondering.  Many polypeptides fall into the range of 20,000-100,000 in their molecular weights.