# What else can the equations tell us?

Continuous form Discrete form Here are a few last questions on interpreting the equations:

### What will the rate of water flow be if permeability is zero?

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• I need a hint ... : Permeability is Pwater.
• ...another hint ... : Zero times anything is zero.

### When will the rate of water flow be the highest?

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• I need a hint ... : the product of three quantities is maximized when each quantity is maximized

### What happens if the osmolarity of the two solutions is the same?

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• I need a hint ... : If the osmolarities are the same, what about the concentrations?

#### I think I have the answer: If OsM B = OsM A, then (OsM B - OsM A) = 0, so NO net osmosis will take place, no matter how large or leaky your membrane.

None of these were really rocket science. The point is that the equation for rate of water flow is simply a formalization of what our intuition tells us should happen. The equation puts intuition into mathematical language!