What Gas Does Vinegar and Baking Soda Make When They React?

Vinegar and baking soda produce carbon dioxide gas (CO₂). The bubbles and foam are CO₂ escaping from the liquid. The reaction also forms water and sodium acetate, a salt that remains dissolved in the liquid.

Vinegar is a mixture of acetic acid and water. Baking soda is sodium bicarbonate. When the two meet, the acetic acid reacts with the bicarbonate. In simple form, the balanced equation is:

Acetic acid + sodium bicarbonate → sodium acetate + water + carbon dioxide

The carbon dioxide is the only gas produced in a meaningful amount by this reaction. It is colorless and odorless at room temperature PubChem: Carbon Dioxide.

Why the mixture fizzes

Acetic acid supplies hydrogen ions, which react with bicarbonate ions in the baking soda. That reaction forms carbonic acid, which quickly breaks down into water and carbon dioxide. As CO₂ forms in the liquid, some dissolves temporarily and some escapes as bubbles. The fizz is easiest to see when the gas leaves the liquid quickly.

The reaction starts when the ingredients mix. How long it fizzes depends on the amounts of vinegar and baking soda, how well they mix, and how much gas remains dissolved in the liquid. Stirring can help the ingredients meet, but it does not create extra carbon dioxide. The total amount of gas is limited by the reactant that runs out first.

Baking soda is sodium bicarbonate, a white crystalline solid that dissolves in water PubChem: Sodium Bicarbonate. Vinegar contains acetic acid, a weak acid that mixes with water PubChem: Acetic Acid. The acid and base react in the water already present in vinegar, so no special conditions are needed.

What affects the amount of gas?

The quantity of carbon dioxide depends on how much sodium bicarbonate and acetic acid are available to react. If there is enough acid, adding more baking soda can produce more CO₂. If the acid is used up first, extra baking soda will remain unreacted and will not make more gas. The same limit applies in reverse: once the baking soda is used up, extra vinegar cannot produce more CO₂.

Temperature can affect how quickly the gas escapes from the liquid. Warmer liquid can release dissolved CO₂ faster, while cooler liquid may retain more of it for a time. Temperature does not replace the need for the reactants, and it does not make more gas than the available acid and bicarbonate can produce.

The gas may be collected briefly in a container, but it mixes with the surrounding air. Carbon dioxide is denser than air, which can help it flow downward during a demonstration, though it does not remain neatly separated for long PubChem: Carbon Dioxide. Do not make the reaction in a sealed container. As gas forms, pressure can build inside and cause the container to leak or burst.

One example: a baking mixture

A batter that contains baking soda and an acidic ingredient can release CO₂ as soon as the wet and dry ingredients are mixed. The gas forms bubbles in the batter. If the batter is baked while those bubbles are still present, they can expand and contribute to the rise. Chemical leaveners produce carbon dioxide for this purpose Chemical Safety Facts: Carbon Dioxide.

The timing matters because this reaction begins before the batter goes into the oven. If the batter sits for too long, some gas can escape, leaving less to help the batter rise. Recipes account for the amounts of acid and baking soda so the mixture can produce the intended amount of gas. Adding extra baking soda does not guarantee a higher rise; if there is too little acid to react with it, some baking soda will be left over.

What remains after the fizzing stops?

The liquid contains water and sodium acetate, along with any vinegar or baking soda that did not react. The amount of each depends on the starting quantities. Sodium acetate is not a gas, so it does not cause the bubbles. The visible fizz comes from carbon dioxide leaving the liquid.

The mixture is not necessarily a pure solution of sodium acetate. If one ingredient was added in excess, some of that ingredient can remain as well. This is why the simplest description of the products applies to the reaction itself, while the leftover mixture depends on how much of each ingredient was used.

Key Takeaways

• Vinegar and baking soda produce carbon dioxide gas (CO₂).
• The reaction also forms water and sodium acetate.
• The amount of CO₂ depends on the available acetic acid and sodium bicarbonate. The ingredient that runs out first limits the reaction.
• Stirring can help the ingredients mix, but it does not increase the total gas the reactants can produce.
• Do not seal the reaction in a container, because pressure can build as CO₂ forms.