Baking Soda: Salt or Base

name         Anna
status       student
grade        9-12
location     HI

Question -   The textbook says that baking soda is a salt and 
that salts are always neutral, but don't we always use baking soda 
as a base? I am so confused.
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Anna,

The chemical composition of baking soda is NaHCO3. You can imagine 
that this could have been produced by the acid-base reaction of the 
base, Na2CO3, with some acid, H+. As such we can consider NaHCO3 a 
salt (by the definition that the product of an acid and a base is a 
salt). However, since NaHCO3 can still react with another H+ to give 
H2CO3, then by the definition that anything that reacts with an acid 
must be a base, then NaHCO3 can be considered a base.

In the end, all these definitions are not as important as your 
understanding that salts are the product of acid-base reactions, and 
that a base (or an acid) is not to be defined by its chemical 
composition but rather in how it reacts or what it reacts with.

Greg (Roberto Gregorius)
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Anna,

Technically baking soda is a mixture of a few things, but the 
primary ingredient is sodium bicarbonate (NaHCO3) and is considered 
a weak base, primarily but is also a salt.  The term salt refers to 
the bonding in the compound and the term base refers to its ability 
to scavange or remove protons from other compounds.  So technically 
you can have a salt that has acid/base properties.  Note that from 
what is explained below that the relation between the compounds you 
have conjugate acids and conjugate bases etc.  If you are unsure of 
these term look them up in your textbook.

There are two basic sites on carbonate and when they are both 
protonated (H2CO3) you have carbonic acid, if one is taken away and 
replaced with a counterion (like sodium) you get NaHCO3 (sodium 
bicarbonate or sodium hydrogen carbonate) and if both protons are 
taken away then you get sodium carbonate Na2CO3).  Sodium carbonate 
is a neutral salt, yet it is the strongest base that I have listed 
of the compounds above.

Matt Voss
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