baking soda (sodium bicarbonate) plus vinegar (acetic acid) yields carbon dioxide plus water plus sodium ion plus acetate ion
The chemical equation for the overall reaction is:
NaHCO3(s) + CH3COOH(l) → CO2(g) + H2O(l) + Na+(aq) + CH3COO-(aq)
with s = solid, l = liquid, g = gas, aq = aqueous or in water solution
Another common way to write this reaction is:
NaHCO3 + HC2H3O2 → NaC2H3O2 + H2O + CO2
The above reaction, while technically correct, does not account for the dissociation of the sodium acetate in water.
The chemical reaction actually occurs in two steps. First, there is double displacement reaction in which acetic acid in vinegar reacts with sodium bicarbonate to form sodium acetate and carbonic acid:
NaHCO3 + HC2H3O2 → NaC2H3O2 + H2CO3
Carbonic acid is unstable and undergoes a decomposition reaction to produce the carbon dioxide gas:
H2CO3 → H2O + CO2
The carbon dioxide escapes the solution as bubbles. The bubbles are heavier than air, so the carbon dioxide collects at the surface of the container or overflows it. In a baking soda volcano, detergent usually is added to collect the gas and form bubbles that flow somewhat like lava down the side of the 'volcano'. A dilute sodium acetate solution remains after the reaction.
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