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So I get that work is done when a net force converts potential to heat or kinetic. But I also understand that osmosis is driven purely by entropic processes. There is no net force, only a statistical change driven by random motion. So where does the energy, aka osmotic power or pressure actually come from. It seems contradictory that it is purely entropic yet releases free energy.

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Purely entropic processes can also be thought of as "gradient-driven" processes. If you'd ask entropy, it would like to homogenize all underlying variables in real space, so gradients will drive homogenization.

And this is how osmosis is driven: Via concentration gradients. If there is a concentration imbalance between two pockets, then they can achieve equal concentration either by exchanging particles, or by exchanging host volume.
In biological processes the semipermeability of semipermeable membranes makes the passage of the larger particles (Sodium ions, Proteins, other nutrients...) impossible if there are no dedicated molecular channels, so the host volume, which is water has to move.

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