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Homework Help: I am sure I am doing this Acid/Base problem wrong

  1. Jul 12, 2016 #1
    What is the pH of a solution made from 34.6 ml if 3.45*10^-4 M of H2SO4 added to 41.7 ml of 4.56*10^-4 M of Al(OH)3?

    I know how to find H+ and OH- and pH I also know how to use x mol / L, but I cannot get them to click together. Everyone keeps telling me to use RICE but my professor never explained what this was to us.

    I keep trying different ways to start this problem and they all look wrong. This is the only problem that I don't even know how to put together from the start.
  2. jcsd
  3. Jul 13, 2016 #2


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    Homework Helper
    Gold Member

    First update the concentrations of acid and base in the total solution of 76,3ml
    Then write down the chemical neutralization reaction between the acid and the base.
    Then calculate how much acid (or it might be base) that will be left. If it is acid that will be left then you can find [H+]* (and [OH-] will follow)
    If it is base that will be left then you can find [OH-] and then [H+].

    * have in mind that extra water will be produced from the neutralization reaction so you should update the concentration of the acid left (or base left).
  4. Jul 13, 2016 #3


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    Staff: Mentor

    What if you were told to start it just as a limiting reagent problem?

    But I don't like this question. Unless you are expected to ignore the Al(OH)3 insolubility and to treat the solution as if Al(OH)3 was completely dissociated (which is not true) finding the answer is pretty tricky.
  5. Jul 23, 2016 #4
    Can we say impossible to solve? The solubility product of Al(OH)3 is absolutely essential.
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