Which side of the membrane has the most salt molecules?

If the membrane is permeable to that molecule, no. It just moves back and forth at the same rate on average over time. If the membrane is actively transporting that molecule in one direction, it will depend how quickly it is being actively transported relative to passive transport in the other direction. Also, once an equilibrium point is reached (whatever that point may be), the permeability of the membrane may be altered (common in biological systems), so sometimes there may be no movement in one or both directions. If it is a one way permeability, then the concentration may become very slightly higher on the destination side than the origin, and the degree to which that is true will depend on the molecule, the thickness of the membrane, other molecules in the system, the energy in the system (and where that energy is), and the nature of the membrane's permeability.

Explanation:

answer; they both highlight the power of the situation in determining behavior;