PUN asked in Science & MathematicsChemistry · 3 weeks ago

Acid/base Conjugation?

I understand the basics of acid/base conjugates. However, I keep struggling to determine what the conjugate acid or base will be from a given acid/base. For ex. if you're given a compound, to determine what the conjugate acid or base would be from it. Are there any tricks or just a simplified summary to memorize and apply it?

3 Answers

  • Dr W
    Lv 7
    3 weeks ago

    acid....proton donor

    base.. proton acceptor

    .. let's look at acetic acid

    CH3CO2H + H2O <-----> CH3CO2- + H3O+

    ... acid.. . .  . 

     proton donor

    CH3CO2H + H2O <-----> CH3CO2- + H3O+

    ....... ... ... ... ... .. .. .. . . ....  base

     .... ... ... ... ... ... .... ... .. proton acceptor

    CH3CO2H and CH3CO2- are conjugate acids and bases


    how about this one

    .. H2PO4- + H2O ---> HPO4(2-) + H3O+

    which is the acid and which is the base?

    are they conjugate acids and bases?


  • 3 weeks ago

    The conjugate base will always be deficient one H+ when compared with the conjugate acid. Or said, the other way, the conjugate acid will have one H+ more than the conjugate base. 

    So, for example, the conjugate base of H2CO3 would be HCO3-. 

    The conjugate base of H2O is OH-.

    The conjugate acid of SO42- is HSO4-

    The conjugate acid of H2O is H3O+

    That help?

  • 3 weeks ago

    First, determine if you're working with an acid or a base.

    If you're working with an acid, the conjugate base is what you get when you remove an acidic proton. Example: HCl => Cl-

    If you're working with a base, the conjugate acid is what you get when you add a proton. Example: NH3 => NH4+

    Note that this is assuming you're working with the Bronsted-Lowry definition of acid and base, not the Lewis definition, but the same concept applies to Lewis acids and bases except you think about the electron flow instead of the protons.

    If you don't know the difference between the definitions, don't worry about it, you're probably using Bronsted-Lowry.

    Hope this helps!

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