Re: Why didn't steel wool rust in baking soda solution

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