When people talk about osmosis, they say that when we add a mole of NaCl, then each its molecule gets dissolved into 2 separate particles and therefore we have 2osM/L solution.
But both Na & Cl are attached to molecules of water which means that those water molecules are not water anymore and they can't penetrate the membrane. Thus not only the presence of Na & Cl itself changes the concentration of water in solution, but also the number of water molecules taken by those particles.
Therefore if we put 1 particle that binds to 1 water molecule and 1 particle that binds to 5 water molecules - they change the water concentration differently.
Please somebody tell me where I'm wrong.