Question

if there line cross concentration (m) twice against the respective percentage from positive to negative then back to positive and then negative again/ how can i calculate and determine the molarity for potato cell?

Answer 1

To determine the molarity of a solution based on the behavior of potato cells in different concentrations, you can use the results from an experiment that involves placing potato slices in various sucrose (or salt) solutions and measuring the change in mass or volume of the potato cells.

Here's how you can approach it step by step:

### 1. Conduct an Osmosis Experiment:

1. **Prepare Solutions**: Create a series of sucrose (or salt) solutions with different molarities (e.g., 0 M, 0.1 M, 0.2 M, 0.3 M, etc.).

2. **Cut Potato Samples**: Take equal-sized potato pieces and measure their initial mass.

3. **Immerse Potato Samples**: Place the potato pieces in each solution and let them sit for a fixed amount of time (usually 30 minutes to an hour).

4. **Measure Changes**: After the time period, remove the potato pieces, blot them dry, and weigh them again to get the final mass.

### 2. Plotting Data:

- **Calculate Percent Change in Mass**: Use the formula

\[
\text{Percent Change} = \frac{(\text{Final Mass} - \text{Initial Mass})}{\text{Initial Mass}} \times 100
\]

- **Create a Graph**: Plot the molarity of the sucrose solutions (x-axis) against the percent change in mass (y-axis).

### 3. Analyzing the Graph:

- Identify where the graph crosses the x-axis. This point represents the point at which there is no net movement of water into or out of the potato cells, meaning the concentration of the potato cell's cytoplasm is isotonic with the solution.

- Generally, the line will cross from positive to negative (indicating a gain in mass when in a hypotonic solution and a loss in mass when in a hypertonic solution).

### 4. Determine Molarity:

- **Isotonic Point**: The molarity at which the line crosses the x-axis (0% change) represents the molarity of the potato cell's cytoplasm.

### Example:

- If your graph shows that the percent change crosses zero at 0.2 M, then you can conclude that the molarity of the solute in potato cells is approximately **0.2 M**.

### Important Notes:

- Make sure your potato samples are uniform in size for consistency in results.
- Conduct trials to ensure reliability of your data.
- Record all data carefully and consider average results for accuracy.

By following these steps, you can accurately determine the molarity of the solute in potato cells using osmotic principles.