At equilibrium in thistle funnel experiment

Options

A. Free energy is maximum
B. Water potential gradient is zero
C. Solution in beaker and in thistle funnel are isotonic
D. 1 and 2

Answer

To analyze the question regarding the equilibrium in the thistle funnel experiment, let's break it down step by step:

### Step-by-Step Solution:

1. **Understanding the Thistle Funnel Experiment**:
- The thistle funnel experiment is designed to study osmosis and the movement of water through a semi-permeable membrane. In this setup, a thistle funnel filled with a sugar solution is placed in a beaker of pure water.

2. **Initial Conditions**:
- Initially, the sugar solution in the thistle funnel has a higher concentration of solutes compared to the pure water in the beaker. This creates a concentration gradient.

3. **Osmosis Process**:
- Water moves from the beaker (where the water potential is higher) into the thistle funnel (where the water potential is lower) through the semi-permeable membrane. This movement continues until equilibrium is reached.

4. **Equilibrium State**:
- At equilibrium, the rate of water entering the funnel equals the rate of water leaving the funnel. The hydrostatic pressure inside the funnel increases as water enters, which eventually balances the osmotic pressure.

5. **Analyzing the Options**:
- **Option 1**: Free energy is maximum - This is not necessarily true at equilibrium.
- **Option 2**: Water potential gradient is zero - This is true at equilibrium because there is no net movement of water.
- **Option 3**: Solution in beaker and in thistle funnel are isotonic - This is also true at equilibrium since the concentrations are equal.
- **Option 4**: One and two - This suggests both statements are true, but since option three is definitively true, we focus on that.

6. **Conclusion**:
- The correct answer is **Option 3**: The solution in the beaker and in the thistle funnel are isotonic at equilibrium.