Suppose that while the reverse osmosis system is running tank B becomes contaminated with salt water such that it ends up with a higher salt concentration than tank A. What would happen if the reverse osmosis system was turned off? A) There would be a net flow of water from tank A to tank B. B) There would be a net flow of water from tank B to tank A. C) Water would flow in equal amounts in both directions.

The correct answer is: A) There would be a net flow of water from tank A to tank B.

Explanation:

Osmosis can be defined as the process by which molecules of a substance (water) tend to move from a region where its concentration is high to a region where is concentration is low across a semi-permeable membrane. The force which causes this movement is called the Osmotic Pressure. Reverse Osmosis can be defined as the process by which molecules of a substance (water) move from a region where its concentration is low to a region where its concentration is high, due to the application of a hydrostatic pressure which is more than the osmotic pressure. In the given example, water is is being separated from the salt dissolved in it by the process of Reverse Osmosis. This results in the accumulation of salt in Tank B and accumulation of pure water in Tank A. Reverse osmosis promotes the movement of water from Tank B (where the water concentration is low but salt concentration is high) to Tank A (where the water concentration is high but salt concentration is low) due to the hydrostatic pressure. Stopping Reverse Osmosis will cause normal Osmosis to occur. Hence, the water will move from tank A (where its concentration is high) to tank B (where its concentration is low) until water concentration in both the tanks become equal.