Question

If a cell A with DPD = 5 bars is connected to cells B,C and D, whose OP and TP are respectively 5bars and 5 bars,10 bars and 4 bars, and 8 bars and 3 bars, the flow of water will be from _______.

• A. C to A, B and D
• B. A and D to B and C
• C. A to B, C and D
• D. B to A, C and D.

Answer 1

The correct option is D

B to A, C and D.

The amount by which diffusion pressure of a solution is lower than its pure solvent is known as Diffusion Pressure Deficit (or DPD). Pure solvent has no diffusion pressure defecit and therefore is DPD is 0. And solvent from here will move to a region of high DPD. Therefore movement will always be from a region of lower DPD to a region of higher DPD.

DPDs of B, C and D are as follows:
B: 5 - 5 = 0 bar
C: 10 - 4 = 6 bars
D: 8 - 3 = 5 bars

B having the least amount of DPD of just 0 bar, water will flow from B to A, C and D. And A and D having a lower DPD of 5 bars, compared to C, which has a DPD of 6 bars, water will flow from A and D to C also.