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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?
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.
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.
The reaction can also be classified as a neutralization since a hydrogen ion is donated by one reactant and accepted by another.
Author: Fred Senese firstname.lastname@example.org