chemistry
posted by ashley .
What mass of sucrose should be combined with 491 g of water to make a solution with an osmotic pressure of 8.70 atm at 270 K? (Assume the density of the solution to be equal to the density of the solvent.)

pi = MRT
Substitute for pi, R, and T. Solve for molarity = M.
Then M = moles/L.]
You know L and M, solve for moles.This assumes that the volume of the solution is the same as the volume of the solvent.
Then moles = grams/molar mass. You know moles and molar mass, solve for grams. 
65.995