MadSci Network: Chemistry
Query:

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

Date: Sat Jan 27 15:24:55 2001
Posted By: David Reibstein, Associate Dean
Area of science: Chemistry
ID: 980534975.Ch
Message:

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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