In the event of a hydrochloric acid spill, baking soda is poured on the acid to prevent damage to surfaces. Baking soda is a weak base; when added to hydrochloric acid, it causes a neutralization reaction so the hydrochloric acid no longer causes damage to other materials. In the event baking soda is not available, the spill is diluted with copious amounts of water.
The reaction between baking soda, also known as sodium bicarbonate, and hydrochloric acid is a double displacement reaction. The reactants combine to form sodium chloride, water and carbon dioxide. The carbon dioxide forms bubbles that cause the mixture to overflow a flask if too much baking soda is added at once. Eventually, as more baking soda mixes with the acid, the bubbles stop forming as the acid reaches the neutral state and is no longer able to provide the hydrogen molecules needed to break down the sodium bicarbonate. Carbon dioxide gas is heavier than air and remains in the flask on top of the liquid layer. Tipping the flask gently allows the gas to pour to another container and extinguish a burning wood splint in a beaker. Baking soda works with acidic ingredients in cooking foods, such as breads to form small bubbles that cause the product to rise.