Buffer calculations

  1. 1. The problem statement, all variables and given/known data
    Buffer solution : CH_3COOH (55 mL) + CH_3COONa (45 mL)
    Ka (CH_3COOH) = 1.76 x 10^-5

    Calculate the expected pH of your buffer solution after it has been dilted by making 10 mL of buffer up to 100 mL with deionized water.

    2. Relevant equations
    Ice charts
    n= c x v
    c= n/v

    3. The attempt at a solution
    I've calculated the pH for other additions of strong acids and strong bases but I'm not sure how to start this one. Little bit confused... Just the first step would be a great help :)
     
  2. jcsd
  3. chemisttree

    chemisttree 3,721
    Science Advisor
    Homework Helper
    Gold Member

    You haven't given enough information to start. You need to know something about the concentrations of acetic acid (55 mL?) and acetate (45 mL?).
     
  4. Sorry, they are both 0.10 M
     
  5. chemisttree

    chemisttree 3,721
    Science Advisor
    Homework Helper
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    Review the Henderson-Hasselbach equation. Hint: pKa = -log[Ka]
     
  6. the question is a little confusing due to the given volumes.i need help how to attempt the question.
     
  7. Borek

    Staff: Mentor

    As chemisttree already wrote: use Henderson-Hasselbalch equation. Start calculating concentrations of both acid and conjugate base. At this stage it will be simple dilution problem.

    (in fact you can solve the problem without calculating these concentrations, but I guess explaining the shorter route will only confuse you more)
     
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