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

  1. Nov 6, 2007 #1
    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?
     
  2. jcsd
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