Why are oxidizing agents acidified?

1 Answer
anor277
Dec 23, 2016

Usually because oxidation reactions tend to specify acidic conditions.

Explanation:

And basic conditions tend to lead to the precipitation of insoluble metal hydroxides.

Metal oxidants, say permanganate, MnO_4^-, or dichromate, Cr_2O_7^(2-) tend to be deployed in acidic media:

MnO_4^(-) +8H^+ + 5e^(-) rarr Mn^(2+) + 4H_2O

Cr_2O_7^(2-) +14H^+ + 6e^(-) rarr 2Cr^(3+) + 7H_2O

So we use H^+ or H_3O^+ in the reaction to represent the actual acidic condtions of reaction. Had the reaction been conducted in A BASIC medium, heavy metal oxides and hydroxides would precipitate out pdq.

If a redox reaction is specified to be in a BASIC medium, it is often easiest to balance the redox reaction in acidic conditions using H^+, and then add HO^- ion to each side of the reaction.

For instance, aluminum metal can be oxidized up to aluminate ion, Al(OH)_4^- in strong base. We could represent this as normal:

AlrarrAl^(3+) + 3e^-, but then we could add 4xxHO^- to BOTH sides of the reaction:

Al +4HO^(-) rarr[Al(OH)_4]^(-) + 3e^-

Charge and mass are balanced in this reaction as required.

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