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Homework Help: Sciences or Math HELP

  1. Nov 17, 2004 #1
    This is what I'm going to call my thread, because I think I might have days where I'll have to post on here if I'm stuck on homework or whatever. And I called it Sciences because I am taking all 30-level sciences, and Math 31.

    In Chem recently, I just had a titration lab, and one of the questions confused me. Here's the question:

    a) Write out the net-ionic equation for the addition of sulfuric acid to the potassium permanganate solution.

    Maybe I made a calculation mistake, but my equation is (I don't know how to make subscripts):

    4MnO4-(aq) + 12H+(aq) -> 4Mn2+(aq) + 6H2O(l) + 5O2(g)

    b) Using your answer in a) to guide you, explain why it would not be a good idea to add the sulfuric acid directly to the potassium permanganate solution during this lab?

    I don't know how to answer this question, except that I don't know how this equation would be possible cause all I have on the left-hand side of the arrow is the SOA (strongest oxidizing agent) and I have no reducing agent with it cause my waters cancelled....and water I know in this question is the SRA (strongest reducing agent). And if I don't have an SRA with the KMnO4 (aq) solution, then how is there an reaction still? I got this question answered wrong cause I said if I don't have my SRA with the SOA on the left hand side of the arrow, there's no reaction?

    Can someone help me answer this question cause I don't understand. Thanks.
  2. jcsd
  3. Nov 17, 2004 #2


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    Homework Helper

    I haven't checked your equation, but assuming it's correct, two things occur to me:

    1) That's an awful lot of gaseous oxygen you're producing there.


    2) As I recall, this is a strongly exothermic reaction.

    Do these two things suggest anything to you?
  4. Nov 18, 2004 #3
    Maybe my equation should be checked....I don't think I did anything wrong though....wait, only this part [4Mn2+(aq) + 6H2O(l) + 5O2(g)] is in the buret now, right? Ugh I'm still confused....
  5. Nov 18, 2004 #4


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    Not quite. The net ionic equation tells you what's actually reacting, not what's left over. The things you take out are, essentially, the things that remain unchanged during the reaction. What's left after the reaction are the things you took out plus the products in the NIE.

    I'm afraid I don't have time to check the equation right now - nor, for that matter, the remaining brain cells. It's been a long day. If no one else does it before I check my email tonight, I'll do it then.
  6. Nov 19, 2004 #5
    Just to make sure....

    Can someone check my equation to make sure it's right?
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