How should the reaction between vinegar and baking soda be classified?

What kind of a chemical reaction occurs when acetic acid (vinegar) and sodium bicarbonate (baking soda) are mixed- combination, decomposition, displacement, or double displacement?
Melissa Mattes 1/13/99

A double displacement reaction (also called a double decomposition or metathesis reaction) has the form

AB + CD AC + BD

where A, B, C, and D are atoms or ions. The reaction between vinegar and baking soda can be written as a double displacement reaction if carbonic acid (H₂CO₃) is considered a product:

HC₂H₃O₂(aq) + NaHCO₃(aq) NaC₂H₃O₂(aq) + H₂CO₃(aq)

Here A, B, C, and D are H⁺, C₂H₃O₂^-, Na⁺, and HCO₃^-, respectively. [1, 2]

However, carbonic acid readily decomposes into carbon dioxide and water,

H₂CO₃(aq) CO₂(aq) + H₂O()

and the carbon dioxide can escape from the solution as a gas.

The combined equation is

HC₂H₃O₂(aq) + NaHCO₃(aq) NaC₂H₃O₂(aq) + H₂O() + CO₂(g)

which doesn't fit neatly into one category, since it is a double displacement followed by a decomposition. When you encounter a reaction that is difficult to classify, consider the possibility that it may be the net or total equation for a sequence of steps.

Notes

1. For double displacement reactions in aqueous solution, there is an additional requirement: if all of the products are soluble, strong electrolytes, then no reaction occurs. H₂CO₃ is a weak acid and so, a weak electrolyte. You can see the reason for this additional requirement when you try to write the net ionic equation for a reaction that involves only strong electrolytes: all of the ions are spectator ions in that case, and there is no net ionic equation.
2. The reaction can also be classified as a neutralization since a hydrogen ion is donated by one reactant and accepted by another. Back

Author: Fred Senese senese@antoine.frostburg.edu

Copyright © 1997-2010 by Fred Senese
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Last Revised 02/23/18.URL: http://antoine.frostburg.edu/chem/senese/101/reactions/faq/classify-vinegar-bakingsoda.shtml