A mixture of NaCl and sucrose (C12H22O11) of combined mass 10.2 g is dissolved in enough water to make up a 250 mL solution. The osmotic pressure of the solution is 8.29 atm at 23°C. Calculate the mass percent of NaCl in the mixture.

Answer 1

This a multistep problem involving simultaneous equations.
pi = i*M*R*T. I is the van't Hoff factor. Substitute and solve for M = molarity.

Then you have two equations.
Let X = grams NaCl
and Y = grams sucrose = SU
equation 1 is X +Y = 10.2

Then mols NaCl + mols SU = total mols so equation 2 is
(X/58.5) + (Y/342) = 0.250 x M (from pi calculation)

Solve the two equations for X and Y.
Then %X = (mass X/10.2)*100 = ?