Hemoglobin is the protein that transports O2 through the blood from the lungs to the rest of the body. In doing so, each molecule of hemoglobin combines with four molecules of O2. If 1.37 g of...

Question

hemoglobin combines with 2.13 mL of O2 at 37°C and 724 torr, what is the molar mass of hemoglobin?

Answer in scientific notation

Answer 1

We are asked to find the molar mass of hemoglobin (Hgb) so we need the mass and the moles. We are given the mass (1.37 g) so we essentially need to find moles of Hgb. We can do this by finding moles of O₂ and dividing that by 4 since four moles of O₂ bind to 1 mole of Hgb.

To find moles of O2, we use the Ideal gas law, PV = nRT and solve for n (moles):

n = PV/RT

P = pressure = 724 torr x 1 atm/760 torr = 0.953 atm

V = volume in L = 2.13 ml x 1 L/1000 ml = 0.00213 L

R = gas constant = 0.0821 Latm/Kmol

T = temp in K = 37º + 273 = 310K

n = (0.953)(0.00213) / (0.0821)(310)

n = 7.98x10^-5 moles of O₂ molecules

moles Hgb molecules = 7.98x10^-5 moles O₂ x 1 mol Hgb/4 mol O₂ = 1.99x10^-5 moles Hgb molecules

molar mass Hgb = g / moles

molar mass Hgb = 1.37 g /1.99x10^-5 moles = 68,844 g/mol (be sure to check the math)