How do I calculate the pka of H2Se?

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  • 6 months ago

    H2Se pKa .....

    The obvious, which hardly deserves a post on YA, is to look up Ka of H2Se and take the "negative log". Keep in mind that there are two Ka's and two pKa's, although the second one is negligible.

    Or it can be done experimentally. Use a pH meter to find the H+ ion concentration of a known concentration of H2Se.

    H2Se(aq) <==> H+ + HSe^-

    [H+] = 10^-pH

    Ka = [H+][HSe-] / [H2Se] = [H+]²/[H2Se]

    pKa = -log([H+]²/[H2Se])

  • 6 months ago

    ...

    look up the Ka for H2Se

    I found Ka = 1.3E-4

    then

    pKa = -log Ka = -log1.3E-4 = 3.89

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  • david
    Lv 7
    6 months ago

    usually a problem will give you a certain concentration of the acid. H2Se, and the pH of that solution. When you know those you can use the formula to calculate pKa

  • Mike A
    Lv 7
    6 months ago

    You can't calculate it. It is determined by experiment. Data is available see the link for example:

    https://en.wikipedia.org/wiki/Hydrogen_selenide

    This gives a value of 3.89 ( scroll down the properties on the right hand side of the screen).

    • pisgahchemist
      Lv 7
      6 months agoReport

      Well, yeah. You can calculate pKa(1) from the experimental data. The hydrogen ion concentration of a known concentration of H2Se.

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  • Anonymous
    6 months ago

    You need some data.

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