Why are oxidizing agents acidified?

1 Answer
Dec 23, 2016

Answer:

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.