Ek 1001 gc #715

[TotalDomination]

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Unlike osmotic potential, water potential is a function of temperature and pressure as well as solute concentration. Wen two solutions are separated by a membrane permeable to water but not solute, water will move from higher water potential to lower water potential. As the hydrostatic pressure of a solution increases, the water potential:

a) decreases because the water molecules have less space and so become more ordered.
b) remains constant because water has no place to move
c) remains constant, because temperature increases
d) increases because the water molecules have more free energy

WHY and how do the water molecules have more free energy???????? what? This question and the answer choices are not making any sense to me.

Please help

 

[polyatomic]

Think of potential and kinetic energy. Holding a block 2 meters off the ground gives the block more potential energy than when you hold it 1 meter above the ground. Thus, when you drop the block, the block that was held at a higher point will end up with a higher velocity as it falls to the earth.

This is the same thing, but in liquid form. They say you have 2 solutions separated by a membrane. If one solution has pure water, and another solution has 2 mol of Na ions (for example), there would be a higher hydrostatic pressure and higher "potential" than if you just had 1 mol of Na ions in the solution. This potential is generated because water wants to move into the salt solution to reach an overall equilibrium.

So we have more "free energy" essentially because we have more potential, or more hydrostatic pressure. Here, increased free energy just means that the water will move more forcefully to the other side. This is the same as calculating the potential energy for a block held above the ground as you increase the height.

 

[sdm33]

can we see that water is moving more random , therefore more free energy ??

 

[TotalDomination]

So...the more water WANTS to move to the side with higher solute concentration, the higher the hydrostatic pressure? That actually makes sense. Higher solute concentration, the more force with which water wants to move.

In the question, when the force with which water moves across the membrane (hydrostatic pressure) increases, the higher the pressure, and as a result, the higher the water potential?