is pKa the same as pH?

Discussion in 'DAT Discussions' started by drzakisadiq, Jul 28, 2008.

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  1. drzakisadiq

    drzakisadiq 2+ Year Member

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    Jun 30, 2008
    just wondering, a bit confused on terminology here.
     
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  3. Albuterol

    Albuterol 7+ Year Member

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    Dec 14, 2007
    North Jersey
    pKa = -log of [Ka]
    pH = -log of [H+]

    Ka is the acid dissociation constant = [H+][A-]/[HA]

    pH= pKa when the conjugate base = weak acid at the half-way point on a titration curve

    the lower the pKa the more acidic the solution is
    the lower the pH the more acidic the solution is
     
  4. drzakisadiq

    drzakisadiq 2+ Year Member

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    Jun 30, 2008
    thanks, so if in a problem i were given the pKa, how would i convert that to pH?
     
  5. PreDent2009

    PreDent2009 5+ Year Member

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    Dec 20, 2007
    They would also have to give you the concentration of the acid and its conjugate base so you could use the henderson hasselbach formula. Otherwise, it would be pretty impossible to derive the pKa. You can however tell whether the acid is strong or weak, etc.

     
  6. Albuterol

    Albuterol 7+ Year Member

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    Dec 14, 2007
    North Jersey
    u can use the henderson-hasselbach equation
    pH= pKa + log [conj base]/[wa]

    im not sure of others but hopefully someone else knows.
     
  7. doc3232

    doc3232 7+ Year Member

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    Feb 15, 2008
    You can compare the two, but they are not the same.
    They are equal only if [HA] = [A-]
     

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