What happens when you mix baking soda with citric acid?

When baking soda (sodium bicarbonate) and citric acid are mixed, they react to form carbon dioxide gas, water, and sodium citrate. The chemical reaction that takes place is:

NaHCO3 + C6H8O7 → CO2 + H2O + Na3C6H5O7

The carbon dioxide gas causes a fizzing or effervescent reaction and the mixture will bubble up. This reaction is commonly used as a leavening agent in baking, where the gas bubbles cause baked goods to rise. The sodium citrate formed as a byproduct is a salt that can contribute a slightly sour or tangy flavor to the mixture.

This reaction is also sometimes used in homemade cleaning products, such as effervescent cleaning tablets or powders. The release of carbon dioxide gas can help to lift dirt and grime, making it easier to clean surfaces.