MadSci Network: Chemistry |
As you correctly point out, rusting is the reaction of iron with oxygen, and this process is promoted by water.� The reason that rusting occurs in vinegar but not baking soda solution is that this reaction is accelerated by the presence of acid.� I answered a similar question about this topic recently: GO HERE.� Acids cause an excess of hydrogen ion, H+, in solution, and, as I explained in that other answer, H+ promotes or accelerates the reaction.��
Now, why is there no rusting in baking soda solution?� Baking soda is known chemically as sodium bicarbonate; its formula is
NaHCO3
In water, sodium bicarbonate separates into its two ions sodium ion and bicarbonate ion.
Na+� and� HCO3-
The bicarbonate ion reacts a little bit with water to make the solution basic:
HCO3- + H2O� -->� H2CO3� +� OH-
These additional OH- ions (hydroxide ions) make the solution basic, or alkaline (the opposite of acidic).� Just as acid promotes rusting, base inhibits or slows down rusting.
I hope this is useful.
David Reibstein
Associate Dean, Albert Dorman Honors
College,
NJ Institute of Technology
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