MARTYN F. CHILLMAID / SCIENCE PHOTO LIBRARY MARTYN F. CHILLMAID / SCIENCE PHOTO LIBRARY
Acid-base reaction with indicator. Reaction in a test tube of lemon juice, baking powder and universal indicator. This is an example of the reaction of an acid (citric acid in lemon juice) and a base (sodium bicarbonate in baking powder). Sodium bicarbonate is also called sodium hydrogen carbonate. The red colour indicates that the mixture is still acidic. As the mixture becomes neutral, the colour will turn green. The reaction itself produces water and large amounts of carbon dioxide gas (bubbles seen here). Sodium bicarbonate is often used in the treatment of acid spillage, and also as a medicinal antacid.
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