Ask A Scientist Chemistry Archive

Question:  Why do vinegar and baking soda react?
 scott m guzik

Answer 1:
Vinegar contains a lot of acetic acid; baking soda is sodium
bicarbonate. When sodium bicarbonate dissolves into the vinegar,
it reacts with water and forms OH-, which reacts with the acetic 
acid (OH- is base) to form water.
 
Short answer: it's an acid-base reaction.
 
Hope that helped!
topper

Answer 2:
The fizz though is the formation of carbon dioxide gas.
Bicarbonate is HCO3-.  The reaction:
HCO3-  +  H+ (from the vinegar) ---> H2CO3 (carbonic acid)
Carbonic acid quickly break into water and carbon dioxide:
H2CO3  --->  H2O  +  CO2
Hence the fizzing.
 jschultz