An everyday explanation

Baking Soda and Vinegar: Why They React and Fizz

WikiAnswerly AI · Updated October 11, 2026 · 7 min read

Written and checked with AI using the references below. This is not human expert review.

Quick answer

Baking soda reacts with vinegar because the acid in vinegar gives a proton to the bicarbonate in baking soda. This makes three things: carbon dioxide gas, water, and sodium acetate. Carbon dioxide is the fizz you see and smell. The gas escapes into the air, which keeps the reaction going. Bicarbonate takes protons from acids very easily, so the reaction happens fast.

The Acid-Base Reaction Behind the Fizz

Baking soda is sodium bicarbonate, a mildly alkaline solid. Its chemical formula is NaHCO₃. Vinegar is a water solution of acetic acid (CH₃COOH). When you combine them, the acetic acid donates a hydrogen ion, called a proton, to the bicarbonate ion. This happens on its own because bicarbonate is a base that readily accepts protons from acids.

The balanced equation for the reaction is:

NaHCO₃ + CH₃COOH → CH₃COONa + H₂O + CO₂(g)

In plain words: one unit of baking soda plus one unit of acetic acid produces sodium acetate (a dissolved salt), water, and carbon dioxide gas. The (g) label on CO₂ means it escapes as a gas, which is exactly what you see as bubbles and foam.

What Each Product Is

Understanding the three products helps you see why the reaction looks and behaves the way it does.

Carbon dioxide (CO₂): This is the gas that makes the mixture fizz and foam. Because it is a gas at room temperature, it leaves the liquid as bubbles. The rapid release of CO₂ is what causes the liquid to foam up and overflow its container in the classic volcano demonstration.
Water (H₂O): Formed as part of the neutralization. It stays in the liquid mixture and is not visible on its own.
Sodium acetate (CH₃COONa): This is the salt produced when an acid and a base neutralize each other. It dissolves in the water and stays in the bowl or container.

How the Proton Transfer Works

Chemists describe this using the Brønsted-Lowry model of acids and bases. In this model, an acid is any substance that donates a proton (H⁺), and a base is any substance that accepts one. Acetic acid is the proton donor here. The bicarbonate ion (HCO₃^–) is the proton acceptor, or base.

When the proton moves from acetic acid to bicarbonate, the bicarbonate breaks apart. It briefly forms carbonic acid (H₂CO₃). Carbonic acid is unstable. It breaks apart almost right away into water and carbon dioxide gas. Water speeds up that breakdown. So the full sequence has two steps:

Acetic acid donates H⁺ to bicarbonate. This forms carbonic acid and acetate.
Carbonic acid decomposes to water and CO₂ gas.

The second step is so fast that you never see carbonic acid accumulate. The CO₂ simply bubbles out. This two-step path is why the generic acid-plus-bicarbonate reaction can also be written as: NaHCO₃ + H⁺ → Na⁺ + CO₂ + H₂O.

Why Baking Soda Reacts With Any Acid, Not Just Vinegar

Baking soda’s bicarbonate ion is amphoteric, meaning it can react with both acids and bases. In water, it makes solutions mildly alkaline. But when it meets an acid, it acts as a base and accepts protons. Vinegar is one of several common acids that trigger this. Others listed in chemistry references include cream of tartar, citric acid, lactic acid, and hydrogen phosphates. That is why baking soda fizzes in buttermilk or lemon juice too, not just in vinegar.

For a practical comparison, see baking powder and when each is used in recipes. The main point is that baking powder already contains a dry acid. So it does not need vinegar or another acidic ingredient to release CO₂.

What You See, Smell, and Feel

The fizzing starts the moment the two substances touch, because the reaction is spontaneous at room temperature. No heat or spark is needed. The foam forms because CO₂ bubbles nucleate throughout the liquid faster than they can escape, trapping liquid between them. If you add dish soap to the mixture (as in the volcano experiment), the soap stabilizes the bubbles and makes the foam last longer and grow larger.

The excerpts do not provide a confirmed enthalpy value for this specific reaction, so the exact thermal effect cannot be stated with certainty here.

One Safety Point: Never Seal the Mixture

If you run this reaction inside a closed bottle or container with no way for gas to escape, pressure builds as CO₂ accumulates. The pressure can become high enough to rupture the container. Always use an open vessel when combining baking soda and vinegar, especially with children nearby.

Illustrative Example: Stoichiometry in a Teaspoon

This is a labeled illustrative example using checked arithmetic. One teaspoon of baking soda is roughly 4 grams (g). The molar mass of NaHCO₃ is 84 g per mole, so 4 g is about 4/84 of a mole. The balanced equation shows a 1:1 ratio, so that amount of baking soda needs the same number of moles of acetic acid to react completely. The molar mass of acetic acid (CH₃COOH) is 60 g per mole. In practice, most kitchen demonstrations use far less vinegar than needed for a complete reaction. So the baking soda is in excess, and some stays unreacted after the fizzing stops.

This explains a common observation. Adding more vinegar to a bowl that has stopped fizzing often restarts the reaction. That happens because unreacted baking soda is still sitting in the bowl.

A Common Misconception: Does Mixing Them Make a Good Cleaner?

Many people mix baking soda and vinegar hoping for a powerful cleaning solution. The chemistry shows why that does not work as expected. The two substances neutralize each other. The acetic acid that gives vinegar its cleaning and deodorizing power is consumed in the reaction, and the alkaline baking soda is also used up. What remains is mostly water and dissolved sodium acetate, which has little cleaning power. Using them separately, one after the other, is more effective than mixing them together. For more on chemistry of everyday substances, the same neutralization principle applies whenever an acid and a base are combined.

Frequently asked questions

Does the reaction use up all the baking soda and vinegar equally?

Not necessarily. The balanced equation shows a 1:1 molar ratio, but household amounts rarely match that exactly. Baking soda is denser and more concentrated per teaspoon than the acetic acid in dilute vinegar, so baking soda is usually in excess. That is why adding more vinegar to a bowl that has stopped fizzing often restarts the reaction.

Why does baking soda also fizz when heated, without any vinegar?

At temperatures above 80 degrees Celsius (176 degrees Fahrenheit), baking soda breaks down from heat alone. Two molecules of NaHCO3 split into sodium carbonate, water, and CO2. No acid is needed. However, this path leaves sodium carbonate behind. Sodium carbonate is strongly alkaline and can give baked goods a bitter, soapy taste if no acid is present to neutralize it.

Is the leftover liquid after the fizzing stops safe to pour down the drain?

Yes. The main products are sodium acetate (a food-grade salt used as a flavoring), water, and any excess unreacted vinegar or baking soda. None of these are hazardous at the small quantities used in kitchen or classroom demonstrations. Standard household drain disposal is appropriate.

Does the same reaction happen with other acids, like lemon juice or buttermilk?

Yes. Baking soda reacts with any acid that can donate a proton to the bicarbonate ion. Citric acid in lemon juice, lactic acid in buttermilk, and tartaric acid in cream of tartar all trigger the same CO2-releasing reaction. This is why recipes use baking soda with acidic ingredients to leaven baked goods.

Why does carbonic acid not stay in the mixture as a stable acid?

Carbonic acid (H2CO3) is highly unstable in water. Water speeds up its breakdown into CO2 and water. The carbonic acid falls apart almost instantly after it forms, so CO2 escapes as a gas rather than staying dissolved in the mixture.

Sources

Sodium bicarbonate - Wikipedia · en.wikipedia.org
Carbonic acid - Wikipedia · en.wikipedia.org
Acid–base reaction - Wikipedia · en.wikipedia.org

Written by AI; checked through automated evidence and editorial review. References retrieved October 11, 2026.

Spotted an error? Tell us what needs correcting.