Facsimile version:

Find the ratio of oxidizing agent to reducing agent which must be preserved in the final balanced equation. You must show how you arrived at your decision; if no work is shown, then no credit will be given. You must, of course, identify the oxidizing and reducing agents correctly.

Mn₂O₇^1- + Ru²⁺ “ RuO₄^1- + Mn²⁺

Solution:

Oxidation numbers assigned:

Mn₂O₇^1- + Ru²⁺ “ RuO₄^1- + Mn²⁺

+6.5, -2 +2 +7, -2 +2

Therefore, at least NINE X electrons must be "gained" to change an integral number of (two manganese atoms) from +6.5 to +2 { ( 2 * [6.5-2]) = 9} (this is a reduction, the Mn₂O₇^1- is the oxidizing agent) , and

at least FIVE Y electrons must be "lost" to oxidize Ru atoms from +2 to +7

{ 2 - 7 = -5} (this is a loss of electrons, therefore an oxidation, and the Ru²⁺ is thereducing agent).

Conclusion: the ratio which must be preserved in the balanced equation is 5 moles of oxidizing agent to 9 moles of reducing agent.

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Note to students: occasionally, as in the case of oxidation by nitrates, some of the nitrate acts as oxidizing agent, and some is used as a spectator ion. This will never be a problem when balancing net equations; if the spectator ions are included, it is a simple matter to add enough to those acting as oxidizing or reducing agents to cover those required to act as spectator ions. Dr. Clippard will NOT ask you to balance an equation where you must consider that the oxidizing or reducing agent in more than one way.

Find the ratio of oxidizing agent to reducing agent which must be preserved in the final balanced equation. You must show how you arrived at your decision; if no work is shown, then no credit will be given. You must, of course, identify the oxidizing and reducing agents correctly.

MnO₄^1- + Ru²⁺ “ RuO₃^1- + Mn²⁺

Find the ratio of oxidizing agent to reducing agent which must be preserved in the final balanced equation. You must show how you arrived at your decision; if no work is shown, then no credit will be given. You must, of course, identify the oxidizing and reducing agents correctly.

MnO₄^1- + Ru²⁺ “ RuO₃^1- + Mn²⁺

Find the ratio of oxidizing agent to reducing agent which must be preserved in the final balanced equation. You must show how you arrived at your decision; if no work is shown, then no credit will be given. You must, of course, identify the oxidizing and reducing agents correctly.

Cr₂O₇^2- + Ru²⁺ “ RuO₄^1- + Cr³⁺

Find the ratio of oxidizing agent to reducing agent which must be preserved in the final balanced equation. You must show how you arrived at your decision; if no work is shown, then no credit will be given. You must, of course, identify the oxidizing and reducing agents correctly.

Cr₂O₇^2- + Ru²⁺ “ RuO₄^1- + Cr³⁺