When copper metal is added to concentrated nitric acid, a vigorous reaction occurs that dissolves the copper, producing a blue-green solution of copper nitrate and releasing brown nitrogen dioxide gas.

1. Place a small amount of copper metal (such as copper turnings or a short length of copper wire) into a fume hood or well-ventilated reaction vessel.
2. Carefully add concentrated nitric acid to the copper.
3. Observe the reaction as the copper dissolves and brown fumes of nitrogen dioxide are released.
4. Note the blue-green solution forming, which contains copper nitrate.

Reaction of copper with nitric acid - Royal Society of Chemistry:

Making Nitrogen Dioxide - Berean Builders:

📄 Occurrence, Preparation, and Properties of Nitrogen - Openstax: https://openstax.org/books/chemistry-2e/pages/18-7-occurrence-preparation-and-properties-of-nitrogen

• Compare the reaction with other metals such as zinc or magnesium to see differences in reactivity.

• This reaction must only be performed in a fume hood due to toxic nitrogen dioxide gas.
• Wear safety glasses and gloves to protect from nitric acid burns.
• Handle concentrated nitric acid with extreme care; it is highly corrosive and oxidizing.
• Do not inhale fumes under any circumstances.
• Dispose of waste solutions properly following local regulations.

• Why does concentrated nitric acid react differently with copper compared to dilute nitric acid? (Dilute acid produces mainly nitric oxide, while concentrated acid produces nitrogen dioxide.)
• What is the oxidation state change of copper in this reaction? (Copper goes from 0 in the metal to +2 in copper nitrate.)
• Why does the solution turn blue-green? (The color is from dissolved copper(II) nitrate.)
• Why must this experiment be performed in a fume hood? (Because nitrogen dioxide is toxic and dangerous to breathe in.)