how do you find out the chlorine level in water after you have found how many drops of silver nitrate is needed to turn 20ml of water combinde with 2.5ml of protasium chromate a permanent red.

To find out the chlorine level in water using the number of drops of silver nitrate required to turn a solution of water and potassium chromate to a permanent red, you will need to perform a series of calculations.

Here is the step-by-step process:

1. First, note down the number of drops of silver nitrate required to turn the solution to a permanent red. Let's say it is 'x' drops.

2. Next, prepare a standard solution of chlorine by taking a known concentration of chlorine (e.g., 100 ppm) in water.

3. Take a small sample of the standard chlorine solution and add 2.5ml of potassium chromate (which acts as an indicator) to it.

4. Titrate the sample with silver nitrate drop by drop until the solution turns a permanent red, just like in the initial experiment. Note down the number of drops of silver nitrate required for this step. Let's call it 'y' drops.

5. Now, calculate the chlorine concentration in the standard solution using the formula:

Chlorine concentration (ppm) = (y / x) * (100 ppm)

Here, 'x' represents the number of drops required to turn the original water sample to a permanent red, and 'y' represents the number of drops required to turn the standard chlorine solution to a permanent red.

6. Finally, you can use this calculated chlorine concentration value to determine the chlorine level in your original water sample.

Note: Titration experiments involving silver nitrate and potassium chromate should be performed with caution, as these chemicals can be hazardous. It is recommended to consult a professional or follow proper lab protocols when conducting such experiments.