Descriptive Chemistry: Copper and Nitric Acid

In this video Mr. Keller demonstrates the reaction between copper metal and concentrated nitric acid. The reaction produces nitrogen dioxide (a reddish-brown gas), copper nitrate, and water. By carrying out the reaction in a test tube connected to a flask containing an acid-base indicator and an aspirator the toxic nitrogen dioxide is drawn safely down the drain. When the gas passes through the acid-base indicator solution it causes it to change colors in a way that shows that the oxide of a non-metal, nitrogen, is acidic.