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Buffers Lab

  1. Oct 15, 2012 #1
    1. The problem statement, all variables and given/known data
    Calculate the theoretical pH of each solution. The first solution was 30.00 mmol of HOAc (acetic acid) and 53.00 mmol of NaOAc. There was no water in this solution.

    2. Relevant equations

    We have to use this equation.
    4AUNT.png

    3. The attempt at a solution

    I'm unsure of what to plug in. I know HOAc is the weak acid and NaOAC is the strong base? But if I only plug those two numbers I'd have a negative number and you can't take the log of a negative number.
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Oct 15, 2012 #2

    Borek

    User Avatar

    Staff: Mentor

    NaOAc is not the strong base, it is a conjugate base of AcOH (or HOAc as you wrote it).

    Equation you have to use... sigh. Another way of isolating students from understanding the chemistry behind the calculation. You need to have concentration (or number of moles) of conjugate base in the nominator and concentration (or number of moles) of the conjugate acid in the denominator. What you have there now is just a way of calculating numbers of moles from the stoichiometry of the neutralization/protonation reactions.
     
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