In the simulation, sodium chloride was able to diffuse through which membrane(s)? (the molecular weight of sodium is 23, chlorine is 35)

Sodium chloride could diffuse through the membranes: 50 MWCO, 100 MWCO, and 200 MWCO.

The molecular weight of the molecule (e.g. globular protein) that is 90% retained by the membrane or the lowest molecular weight solute (in daltons) in which 90% of the solute is retained by the membrane is called the molecular weight cut-off or MWCO. It is noted that the smaller the MWCO, the tighter the membrane pore size. Since the molecular weight of sodium is 23, chlorine is 35, then they’d diffuse thru the membranes 50, 100, and 200 (since they would be rejected because they have a much lower molecular weight).

that's what i got you can count the number of atoms