How can I use oxidation numbers to identify what element is being reduced and oxidized in the following reactions?H2O2+2Fe(OH)2 -> 2Fe(OH)3   2PbO+C->2Pb+CO2  NiO+H2->Ni+H20 I need to...

How can I use oxidation numbers to identify what element is being reduced and oxidized in the following reactions?

H2O2+2Fe(OH)2 -> 2Fe(OH)3  

2PbO+C->2Pb+CO2 

NiO+H2->Ni+H20

I need to identify reducing agents and show all work.

Asked on by punkboy293

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ncchemist | eNotes Employee

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For the first reaction, the iron (Fe) atom starts in the 2+ oxidation state and ends in the 3+ oxidation state.  We know this because the hydroxide ion (OH) always has a 1- charge.  Since it's oxidation number increases, the iron is oxidized.  The oxygen in the hydrogen peroxide (H2O2) is reduced to water as a product (which you do not have listed).

For the second reaction, the lead (Pb) starts in the 2+ oxidation state because oxygen is most commonly found in the 2- oxidation state.  In the product the lead is in the neutral, or 0, oxidation state, therefore it has been reduced to gain two electrons.  The carbon atom is oxidized to the 4+ state to bond with oxygen and form carbon dioxide.

For the third reaction, the nickel (Ni) starts in the 2+ oxidation state and converts to the 0 oxidation state in the product.  It has therefore been reduced.  The hydrogen gas (H2) has been oxidized to bond with oxygen to form water.

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