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Acid equilibrium constant confusion

Discussion in 'MCAT Study Question Q&A' started by bentonj002, Oct 30, 2014.

  1. bentonj002

    bentonj002

    33
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    Jul 2, 2014
    I know that Ka = [H+][A-]/[HA]. By that equation Ka would also = [H+]^2/[HA] since when HA dissociates it dissociates into equal parts H+ and A- correct? I think I'm just over thinking the whole thing, but I would just like to make sure. Thank you.
     
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  3. Cawolf

    Cawolf 2+ Year Member

    3,349
    2,052
    Feb 26, 2013
    It would if it was dissolving in a solution of pure water.

    But since you want to apply the mass expression to buffers and non-pure solutions it is best to see how common ions effects the acid dissociation.

    So if you put the acid in a solution that already contained protons, you need to proper expression to calculate the dissociation.
     
  4. bentonj002

    bentonj002

    33
    2
    Jul 2, 2014
    Ok, that's what I thought. Thank you for clearing that up for me.
     

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