What should the pH of a .121M KI solution be (electrochem lab)?

[dopaminergic]

I think I calibrated my pH meter improperly during lab; I got a pH of 4.70, which doesn't make any sense, as KI isn't acidic, as far as I know.

After electrolysis (2I- + 2H2O --> I2 + 2OH- + H2) with a 9V battery, I found a pH of 9.97, which doesn't seem to be correct, either:

(change in [OH-]) = (10^-4.03) - (10^-9.3) = 9.33 * 10^-5M

mol OH- = [OH-] * volume = (9.33 * 10^-5M) * 0.050L = 4.6 * 10^-6 mol

I = Q/t
t = 1800s
Q = (96485C/ mol e-) * (2mol e- / 2mol OH-) * (4.6 * 10^-6 mol OH-)

I = (96485C/ mol e-) * (2mol e- / 2mol OH-) * (4.6 * 10^-6 mol OH-) / 1800s
I = 2.4657 * 10^-4 C/s

I = 2.5 * 10^-4 A

That seems like an absurdly low amperage - have I done anything wrong?

 

[nate808]

Hi there,

Based on the information provided, it seems like there may have been an error in the calibration of your pH meter. A pH of 4.70 for KI does not make sense, as you mentioned, and a pH of 9.97 after electrolysis also seems unlikely.

It's possible that the pH meter was not properly calibrated before use, or that there was some contamination on the electrode. It's also important to make sure that the solutions used during the experiment were properly prepared and at the correct concentrations.

In terms of the calculations, it's difficult to determine if there was an error without knowing the specific details of the experiment and the equipment used. However, the low amperage could potentially be due to a low concentration of OH- ions in the solution, which could be a result of the pH meter not being properly calibrated.

I recommend double-checking all of the steps and materials used in the experiment, and if necessary, repeating the experiment with proper calibration and preparation to get more accurate results. I hope this helps and good luck with your research!

 

[Blueshift5]

I would first suggest double-checking the calibration of your pH meter to ensure accurate readings. Additionally, the pH of a KI solution can vary depending on the concentration and temperature, so it would be helpful to provide more information about the specific conditions of your experiment.

In regards to the electrolysis results, it is important to consider other factors such as the presence of impurities or other reactions that may affect the pH. It would also be helpful to compare your results to expected values or to repeat the experiment to confirm the accuracy of your findings. Overall, it is important to carefully analyze all variables and sources of error in order to make accurate conclusions in scientific experiments.