The process of osmosis ceases when

Options

A. Free water become equal
B. the level of water falls
C. Solution are isontonic
D. There is no light

Answer

**Step-by-Step Text Solution:**

1. **Understanding Osmosis**: Osmosis is the movement of solvent molecules (usually water) from an area of lower solute concentration to an area of higher solute concentration through a semi-permeable membrane. This process continues until equilibrium is reached.

2. **Identifying When Osmosis Ceases**: The question asks when osmosis stops. This occurs when there is no net movement of water molecules, which typically happens when the concentrations of solute on both sides of the membrane are equal.

3. **Analyzing the Options**:
- **Option 1: Free water becomes equal**: This option suggests that osmosis stops when the free water molecules are equal. However, free water refers to water molecules that are not bound or restricted, and equal amounts of free water do not necessarily indicate that osmosis has ceased.
- **Option 2: The level of water falls**: This option implies that osmosis stops when the water level falls. However, a decrease in water level does not directly correlate with the cessation of osmosis, as water potential (psi w) does not play a role in stopping the process.
- **Option 3: Solutions are isotonic**: This option states that osmosis ceases when the solutions on both sides of the membrane are isotonic, meaning they have the same concentration of solutes. In this case, there is no concentration gradient, and thus no net movement of water occurs.
- **Option 4: There is no light**: This option suggests that the absence of light affects osmosis. However, light does not impact the process of osmosis directly; it may influence other processes like photosynthesis but not osmosis itself.

4. **Conclusion**: Based on the analysis of the options, the correct answer is **Option 3: Solutions are isotonic**. Osmosis ceases when the concentrations of solute on both sides of the membrane are equal, resulting in no net movement of water.

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