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Homework Help: Chemical reactions

  1. Oct 5, 2009 #1
    I was wondering how come when ever there's a question like aluminum reacts with bromine it is usually written like Al + Br2? or Potassium reacts with oxygen is K + O2?

    How do we know when there's 2 of them?? Is there like a special rule? Why isn't there K2 or Al2??
  2. jcsd
  3. Oct 5, 2009 #2
    Those are not chemical equations. AlBr3 & K2O2 are though. Al forms +3 ions so you would need three -1 bromide ions to balance the charge.
  4. Oct 5, 2009 #3
  5. Oct 6, 2009 #4


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    Staff: Mentor

    They were not inteded to be 'equations'.

    No - these are 'formulas'.
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