Last week, I did titration of Zn with EDTA experiment. I used calmigte as the indictor. The endpoint of this titration is supposed to be blue. The color change go from wine-red to violet to Blue. I did a mistake by stopping the titration at the violet color. Anyway I can estimate how many mL I am away from the Blue end-point. Thanks.

Question

Last week, I did titration of Zn with EDTA experiment. I used calmigte as the indictor. The endpoint of this titration is supposed to be blue. The color change go from wine-red to violet to Blue. I did a mistake by stopping the titration at the violet color. Anyway I can estimate how many mL I am away from the Blue end-point. Thanks.

Answer 1

So what's the question?

Answer 2

I meant to say "Is there anyway to estimate how many mL I am away from the blue endpoint. Thanks

Answer 3

To estimate how many mL you are away from the blue endpoint, you can perform a back titration using a standard solution of zinc. Here's how you can proceed:

1. Prepare a standard solution of zinc with a known concentration. You can use a zinc salt, such as zinc sulfate or zinc chloride, and prepare a solution of a known concentration, for example, 0.1 M.

2. Take a known volume of your sample solution from the violet endpoint and transfer it to a flask. Make sure you accurately measure the volume.

3. Add an excess of the standard zinc solution to the flask. The excess of zinc will ensure that all of the EDTA in your sample gets complexed.

4. Now, add the calmagite indicator to the flask and titrate the excess zinc using a solution of EDTA of known concentration. The calmagite will change the color of the solution as the EDTA displaces the excess zinc.

5. Continue titrating until you observe a color change from violet to blue, which you missed during the original titration. Make sure you record the volume of EDTA required for this color change.

6. Finally, subtract the volume of EDTA used in this back titration from the total volume used in the original titration. The difference will give you an estimate of the volume (in mL) by which you missed the blue endpoint.

For example, let's say you used 25 mL of sample solution in the original titration and performed a back titration that required 5 mL of EDTA to reach the blue endpoint. In this case, you missed the endpoint by 5 mL.

Remember to repeat the back titration several times to ensure accuracy and calculate an average value.