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-   -   Balance the following redox reactions using half-reaction method. (https://www.askmehelpdesk.com/showthread.php?t=419129)

  • Nov 24, 2009, 08:49 PM
    sarah1004
    balance the following redox reactions using half-reaction method.
    1) Mg+N2---->Mg3N2
    3Mg+N2----->Mg3N2
    I really don't know how to do this one..

    2) Cu^2+ + Al----->Cu+Al^3+
    2e+Cu^2+ ----> Cu X3
    Al------>Al^3+ + 3e X2
    6e+3Cu^2+ -----> 3Cu
    2Al----->2Al^3 + 6e
    6e+3Cu^2+ + 2Al ------------------> 3Cu+2Al^3 + 6e
    3Cu^2+ + 2Al ------------------> 3Cu+2Al^3
    I am not sure about this one either..

    3) H2+Ag^+ ---->Ag+H^+
    H2+Ag^+----------->Ag+2H^+
    H2----->2H^+ +e
    e+Ag^+----------->Ag
    H2+e+Ag^+----------->2H^+ +e+Ag
    H2+Ah^+ ------------> 2H^+ +Ag

    I am not sure about all of above questions..
    So, Please help me Thanks
  • Nov 25, 2009, 09:56 AM
    Unknown008

    1 & 2 are correct.

    For 3, you missed something:



    Now, you should be able to correct it.

    Anyway, checking the charges on the right and left sides from your given answer, you have +1 on the left and +2 on the right. :)
  • Nov 28, 2009, 11:50 PM
    sarah1004
    So, I think number 3 is going to be
    2H2 + Ag^+ ------------------------> 2H^+ + Ag

    Thanks!
  • Dec 1, 2009, 03:18 AM
    Unknown008

    Hmm, you have 4 H on one side and only two on the other...

    Ok, put one equation above the other like this:




    Multiply the first one by two and add up, giving:


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