Question

The osmotic pressure of seawater is 1.05 atm. Four experiments were carried out as shown in the table. In which of the following experiments, pure water can be obtained in part-II of the vessel?
 

• A. \( I, III \) only
• B. \( II, IV \) only
• C. \( I, II, III, IV \)
• D. \( IV \) only

Hint:

- Reverse osmosis occurs when external pressure osmotic pressure of a solution. - For pure water to be collected, pressure applied on seawater must be higher than 1.05 atm. - If no pressure is applied in part-I, reverse osmosis will not occur.

Answer 1

The Correct Option is A

Reverse osmosis is used to obtain pure water from seawater. To achieve this, a pressure greater than the osmotic pressure of seawater (1.05 atm) must be applied to the seawater side (part-I). This forces water molecules to move from the seawater side (part-I) to the pure water side (part-II) against the osmotic pressure gradient.

In experiments I and III, pressure is applied to part-I. Since the applied pressures (10 atm and 15 atm) are greater than the osmotic pressure of seawater (1.05 atm), pure water will be obtained in part-II in these experiments.

In experiments II and IV, pressure is applied to part-II (pure water side). Applying pressure on the pure water side would have no effect on the flow of water from seawater to the pure water side and hence, pure water is not obtained in part-II.

Therefore, pure water can be obtained in part-II only in experiments I and III.