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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: Triglyceride on April 11, 2011, 12:47:17 PM

Title: Could someone double check my answer? Osmotic pressure & molar mass
Post by: Triglyceride on April 11, 2011, 12:47:17 PM

A solution was made by dissolving 5 mg of hemoglobin in water to give final volume of 1.00 mL. The osmotic pressure of this solution was 1.91 x 10^-3 atm at 25C. Calculate the molar mass of hemoglobin.

pi = iMRT
i = 1 since hemoglobin is nonelectrolyte and doesn't dissociate
T = 298 K
R = constant = .0821 L atm/mol K

1 mL => .001 L
5 mg => .005 g

1.91 x 10^-3 = MRT = (.0821 L atm/mol K)(298 K)(M)

I plugged everything in and ended up with 64046.6 g/mol. Seems a bit high for me. Thank you.

Title: Re: Could someone double check my answer? Osmotic pressure & molar mass
Post by: tamim83 on April 11, 2011, 01:33:14 PM

That's actually fairly close.  Wikipedia says its around 68,000 daltons (or amu).  Your math seems to be fine.