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Homework Help: Conjugate pairs

  1. Jan 17, 2016 #1


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    1. The problem statement, all variables and given/known data
    Which pairing is not a set of conjugates?

    A. OH1– and H2O
    B. HC2H3O2 and C2H3O21–
    C. HCl and Cl1–
    D. NH3 and NH41+
    E. H2SO4 and SO42–

    2. Relevant equations

    3. The attempt at a solution
    I couldn't choose because conjugates, from what I learnt, is basically an acid or a base and its equivalent with more or less protons. All of the pairs have protons as their only difference. The only special case is E with 2 proton difference, but I know H2SO4 is sulfuric acid and when it has donated its protons it will become SO42–. So it seems to me E would also be conjugate. However, the answer is E. Could someone explain to me why E is not a pair of conjugates?
  2. jcsd
  3. Jan 17, 2016 #2


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    Staff: Mentor

    That's imprecise. Acid and its conjugate base differ by exactly one proton.

    Please remember, that sulfuric acid dissociates stepwise:

    H2SO4 ↔ HSO4- + H+


    HSO4- ↔ SO42- + H+

    Can you show now conjugate pairs in this process?
  4. Jan 17, 2016 #3


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    I see thanks Borek
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