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Homework Help: How do i determine which valence is being used (balancing equations)

  1. Jul 29, 2011 #1
    In balancing chemical equations, we are given lets say the reactants side of the equation and asked to find the products and balance if neccesary, if a metal(usually transition) has multiple valences, how do i know which of the valences is being used?

    this has given me trouble to no end @_@
  2. jcsd
  3. Jul 29, 2011 #2
    for instance look at this, Au has a valence of +1, +2 and +3 so how would i know beforehand which valence they are using? This equation is already balanced and the work is done for us, but in case it isnt, how do i determine that?
  4. Jul 29, 2011 #3
    here we go

    I know the polyatomic ions have only 1 valence so thats not the problem, the sulphate has a valence of 2

    This is a website i got off someone on these forums a few days ago, it shows what i am talking about, some of them have several valences..


    hope you can see the attachment i have linked in this thread.

    Attached Files:

  5. Jul 29, 2011 #4
    You know the valence by looking at the salts shown. For instance, in Au2(SO4)3, the valence of the gold has to be +3 for each gold ion to balance the +2 of each of the 3 sulfate ions. The bromide salts are even easier.
  6. Jul 30, 2011 #5
    pmsrw is correct. If they are giving it to you as a free metal the valence is 0. Otherwise you look at the compound it is in.
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