More Info: When reactive compounds are in the same solution, the activity that occurs is driven by the pursuit of order or stability. The least reactive state of a mixture of baking soda and vinegar in the presence of water is when the products of the reaction form. The ions formed seek to form molecules that are not charged. In this case, the baking soda produces a positively charged sodium ion and a negatively charged hydrogen carbonate molecule. The vinegar produces a positively charged hydrogen ion and a negatively charged acetate ion. The hydrogen ion and the carbonate molecule bond forming carbonic acid which decomposes very readily to carbon dioxide gas (CO2) and water (H2O). The remaining ions form sodium acetate.
Experiments with baking soda and vinegar are readily available everywhere. The experiment can be used to show the volume expansion of a gas by blowing up a balloon placed over a bottle containing the reaction. It can also show the difference between solutions and reactions, because the reaction is not reversible in the classroom.