Question

What is the osmolality of 1.1% NaCl salt solution? How can I calculate this?

Answer 1

First calculate the molality.
m = mols NaCl/kg solvent.

1.1% NaCl = 1.1 g NaCl/100 g solution. That is 1.1 g NaCl/98.9 g H2O) = 1.1 g NaCl/0.0989 kg H2O.
mols NaCl in 1.1 g = 1.1/58.45 = 0.0188

mols NaCl = g NaCl/molar mass NaCl = about 1.1/58.45 = about 0.0188.
Then m = mols NaCl/kg solvent = 0.0188/0.0989 = ?
The van't Hoff for NaCl is 2 (two particles per mol NaCl) so the osmolality is 2*0.0188. Check my calculations and significant figures as well as molar mass NaCl.