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Homework Help: This lab is driving me crazy

  1. Oct 6, 2006 #1
    im takign AP CHEM and i love the course, but we did this one lab. i did the math and came up with the coefficients with the reactants. i'm supposed to compare it to the actual equation, but i can't find it anywhere. the lab included mixing a solution of hypochlorite ions and a solution of thiosulfate ions in a hydroxide solution. well...the hypochlorite and thiosulfate are attached to sodium, but she said not to include those at all in our equations. this is what i have:

    .5M solution OCl- = x/.035L
    x = .0175 mol OCl-

    .5M solution S2O3- = x/.015L
    x = .0075 mol S2O3-

    so i ratioed the moles and got a 2 OCl : 1 S2O3 .

    now all i have to do is find the actual balanced equation and compare it...but i have no clue what the actual equation was and my teacher said to find it online. i searched and searched, but have ended up with nothing. i tried to come up with my own equation which fits this ratio and that is:

    2OCl + S2O3 + 6OH --> Cl2 + 2SO4 + 3H2O

    this equation matches my ratio that i got, but she said that our ratios may be wrong and to just find the actual equations online because we haven't gotten into redox yet. anyway, all or any help would be greatly appreciated.
  2. jcsd
  3. Oct 6, 2006 #2
    looks like redox because of hydroloysis (Na eliminated from equation)...hmmm, i think if that's what you came up with--it really doesn't look wrong to me since you included all the main elements in the mix...
  4. Oct 6, 2006 #3


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    Did you happen to employ iodine reagents at any time during the experiments?
  5. Oct 6, 2006 #4
    im good

    nope, no iodine.

    i'm good, that steve guy told me my equation was fine, so i'm taking his word for it...we haven't covered redox in class yet, so i'm hoping we get to it soon. i thought my equation was good, but i didn't think it was right because it has Cl2 and thats not good. apparently, the Cl2 is dissolved in water, so it's okay.

    thanks for your help though

    -coolest person you'll ever meet :biggrin:
  6. Sep 16, 2007 #5
    i think this is the equation for it:

    4OCl + S2O3 = 4Cl + SO3 +SO2 +O2

    should be a 4:1 ratio.
    Good luck
  7. Aug 14, 2009 #6
    Hey Chemnerd08, I am in AP Chem right now and we just did this exact experiment. I would like to know how you got your answer. I know its the right answer, but I do not fully grasp the concept and would like you to demonstrate the formulas for me.
  8. Aug 15, 2009 #7


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    shfty46 - do not be surprised if chemnerd08 gives you no response because his post was from 2 years ago, and he only made 1 post.

    Check your General Chem. or your Analytical Chemistry textbook about redox reactions. The hypochlorite is being reduced and the thiosulfate is being oxidized. Write each balanced half-reaction. Balance the reactions according the number of electrons needed, in other words, rewrite either or both half-reactions so the electron transfers balance. The rest, I forget for right now; balance the reaction using required Hydrogens, Oxygens, water,
  9. Aug 15, 2009 #8
    Thanks a bunch. After thorough research in my book I finally found a little tid bit on redox. It really made all the difference. Thanks.
  10. Oct 26, 2010 #9
    Hey, this reaction need not produce Cl2 gas! It appears in Wikipedia, and the correct mole ratio is 4:1 (hypochlorite to thiocyante).
    Here is the Wikipedia page URL
    and here is the equation!
    4 NaClO + Na2S2O3 + 2 NaOH → 4 NaCl + 2 Na2SO4 + H2O
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