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Homework Help: Concentation of Citric Acid in Fruit Juice

  1. Sep 11, 2010 #1
    1. The problem statement, all variables and given/known data
    This is a lab for Chemistry in grade 12.

    I'll give some basic info I have.

    Juice substance is Tang.
    A solution of juice is prepared by dissolving 4.00 grams of crystals in 100.0 mL of solution. The juice solution is then titrated using a given solution of sodium hydroxide. Phenolphthalein is used as an indicator.

    Here is my observations,

    Trial # NaOH(aq) added (mL)
    Trial 1 3.31
    Trial 2 3.18
    Trial 3 3.27

    2. Relevant equations
    a) find mol/L of acid (I can do this but I cannot figure out the balanced equation)
    b) how many grams of pure citric acid is in 100 g of tang (as a percent mass)
    *Citric Acid is in your databook. Assume it loses 3 hydrogens.
    My teacher said you shouldn't need the formula of the Tang


    3. The attempt at a solution

    This is all I can think of, I do not know what it will turn into.

    C3H5O(COOH)3(aq) + NaOH(aq) ==>
     
    Last edited: Sep 12, 2010
  2. jcsd
  3. Sep 12, 2010 #2

    Borek

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    Staff: Mentor

  4. Sep 12, 2010 #3
    I think I understand it more now!

    Let me see,

    C3H5O(COOH)3(aq) + 3 NaOH(aq) ==> C3H5O(COO)3(aq) + 3 H2O(l) + 3 Na(s)

    But there wasn't any solid from the reaction so I'm not sure where the Na(s) goes, does it just separate or get added onto one for the formula's?
     
    Last edited: Sep 12, 2010
  5. Sep 12, 2010 #4

    Borek

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    Staff: Mentor

    No no, that was completely wrong. Your product will be a sodium salt!
     
    Last edited by a moderator: Aug 13, 2013
  6. Sep 12, 2010 #5
    What? Now I'm confused again, how does that work? Please tell me asap, I don't have long until I have to have this lab complete.

    Why would it be NaCl? That doesn't make sense with anything. Cl wasn't even part of the experiment. It can't be created through thin air.

    C3H5O(COOH)3(aq) + 3 NaOH(aq) ==> C3H5O(COO)3(aq) + 3 H2O(l) + 3 Na(s)

    This makes sense to me, I don't know where NaCl would go.
     
    Last edited: Sep 12, 2010
  7. Sep 12, 2010 #6
    A salt in chemistry isn't necessarily table salt (NaCl) but an ionic compound you get, along with water, after the neutralization of an acid and [STRIKE]salt[/STRIKE] base.

    You wouldn't actually have C3H5O(COO)3(aq) and Na(s), but rather C3H5O(COO)33-(aq) and Na+(aq). The first one ionized since it lost H+ ions while the Na is still an Na+ ion. It could also be written as Na3C3H5O(COO)3(aq)
     
    Last edited: Sep 13, 2010
  8. Sep 13, 2010 #7

    Borek

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    Staff: Mentor

    Bohrok already nicely explained what is going on. Salt name is sodium citrate.
     
    Last edited by a moderator: Aug 13, 2013
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