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Topic: Redox rxn  (Read 3584 times)

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ygao85

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Redox rxn
« on: June 13, 2005, 10:21:16 PM »
When we are given a bunch of reaction how do we know which one is a redox reaction? Is there any trick that can tell you right away that a reaction is a redox rxn.

Also why is this eqn not a redox rxn:
Cr2O72-(aq)+2OH-(aq)-->2CrO42-(aq)+H2O(l).

Thank you.

Offline xiankai

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Re:Redox rxn
« Reply #1 on: June 14, 2005, 12:02:09 AM »
one quick way to determine is see if there is any change in valency /oxidation number in anyone of the reactants.

your eqn is not redox becos Cr2O7 2- has chromium in 6+ oxidation state, but CrO4 2- also has chromium in 6+ oxidation state.

same goes for hydroxide. oxygen and hydrogen have no changes in valency/oxidation state.
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