Question

When 0.10 g of insulin is dissolved in 0.200 L of water, the osmotic pressure is 2.30 Torr at 20°C. What is the molar mass of insulin?

I tried using the van't hoff equation, converting Torr into atm; but not sure how to do it. my teacher didn't really explain this type of prob yet it's on my homework.

Answer 1

pi = osmotic pressure.
pi = MRT
Convert 2.30 torr to atmospheres (divide by 760), use 0.08206 for R and plug in Kelvin (293 K) for T. Solve for M = molarity.
M = moles/L
You have M from the above, and you have L from the problem, solve for moles.
You know n = grams/molar mass and the problem gives you grams. Calculate molar mass. Post your work if you get stuck.

Answer 2

Do you have to divide again by 760?