Chemical potential vs hydro-static pressure during osmosis

In summary, osmosis is the movement of solvent from a higher to a lower chemical potential across a semipermeable membrane, resulting in a difference in levels of fluids. This may seem to contradict the laws of hydro-statics, but in equilibrium, the chemical potential of the solvent must be equal on both sides, leading to a difference in pressure and overcoming the hydro-static forces. In a u-tube manometer setup with a semipermeable membrane at the bottom, the exchange only takes place through the membrane, with the chemical potential of the solvent depending on the concentration of the solute and pressure. In equilibrium, the chemical potential of the solvent is balanced by the gravitational potential energy, resulting in different pressures for different concentrations of
  • #1
Urmi Roy
753
1
So when osmosis between two solutions (separated by a semipermeable membrane),takes place, the solvent travels from the side where its chemical potential is higher to the side where its chemical potential is lower.
However, this results in a difference of levels of fluids across the membrane.

Doesn't this contradict the laws of hydro-statics? Is chemical potential enough of a driving force to overcome hydro-static forces?

Thanks a lot!
 
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  • #2
Can you describe the setup of the system you are interested in? Typically one is interested in systems where the exchange takes place only through the membranes.
 
  • #3
Yeah, I'm just considering a system in which a structure that looks like a u-tube manometer, but with a semipermeable membrane at the bottom of the 'U' shape, which separates 2 solutions and supposed the one on the left is more concentrated. The exchange does take place only via the membrane.
 
  • #4
Yes, the forces are quite large. The chemical potential of the solvent depends on both the concentration of the solute and the pressure. In equilibrium, the chemical potential of the solvent has to be equal on both sides, hence for different concentrations of the solute, pressure has to be different, too.
 
  • #5
DrDu said:
Yes, the forces are quite large. The chemical potential of the solvent depends on both the concentration of the solute and the pressure. In equilibrium, the chemical potential of the solvent has to be equal on both sides, hence for different concentrations of the solute, pressure has to be different, too.

The hydro-static forces are basically due to the weight of fluid column, so when chemical equilibrium is established, is it like the gravitational potential energy is just balanced by the chemical potential energy?
 

1. What is chemical potential in osmosis?

Chemical potential is a measure of the energy required to transfer a solute from one side of a semi-permeable membrane to the other during osmosis. It is influenced by the concentration of solute particles and the temperature of the solution.

2. How does hydrostatic pressure affect osmosis?

Hydrostatic pressure is the force exerted by a fluid on the walls of its container. In osmosis, hydrostatic pressure can counteract the movement of water across a membrane, reducing the net flow of water. This can occur when the solute concentration is higher on one side of the membrane, creating a pressure gradient.

3. What is the relationship between chemical potential and osmotic pressure?

Chemical potential and osmotic pressure are directly related. As the chemical potential of a solute increases, so does the osmotic pressure. This means that as the concentration of solute particles increases, the force required to prevent water from moving across the membrane also increases.

4. How does temperature affect the chemical potential in osmosis?

Temperature plays a significant role in determining the chemical potential during osmosis. As temperature increases, the kinetic energy of water molecules also increases, leading to a higher rate of movement across the membrane. This can result in a higher chemical potential and a greater tendency for water to move from areas of low solute concentration to areas of high solute concentration.

5. What is the difference between osmotic pressure and hydrostatic pressure?

Osmotic pressure is the pressure required to prevent the movement of water across a semi-permeable membrane due to differences in solute concentration. Hydrostatic pressure, on the other hand, is the force exerted by a fluid on the walls of its container. While both can affect osmosis, they are caused by different factors and have different effects on the movement of water across a membrane.

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