Ion-Electron Method of Balancing Redox

HungryJoe
Mon, 28 May 2012 00:27:21 +0000

Sure.

Take for instance, the half reaction Cr2O7 2- ==> Cr 3+, which takes place in acidic reactions. You won’t need to know how to derive the complete half reaction (that’s more of an AP chemistry area), but you should be able to recognize whether they’re acidic or basic, oxidizing or reducing, and how many moles of electrons are present.

You should also be able to balance the reactions when given all of the reactants and products, but need to fill in the coefficients. Remember to take into account the charges on each side. They must be equal (But not necessarily 0).

Fully balanced half reaction above is 6e(-) + 14H(+) + Cr2O7(2-) ==> 2Cr(3+) + 7H20.
It is acidic, being reduced, and there are 6 moles of electrons.