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Copper and Nitric Acid Chemistry Demonstration

Copper and Nitric Acid Chemistry Demonstration

The copper and nitric acid reaction is a dramatic color change chemistry demonstration. The reaction illustrates several chemistry principles, including exothermic reactions , redox reactions , coordination complexes, oxidation, oxidation states , and the metal activity series . Here are instructions explaining how you perform this demonstration safely, with a look at its chemical reactions.

You only need two common chemicals. The most important part of the reaction is the choice of reaction vessel. The reaction produces heat, so use a study glass container.

  • 40 ml concentrated nitric acid (HNO 3 )
  • 1-liter flask (Erlenmeyer, boiling flask, or Buchner flask)
  • Clamp stand
  • Bowl (optional)

The original demonstration uses a copper penny, but modern pennies are zinc plated with a thin layer of copper. A better choice is a piece of copper wool or some copper shavings. The reaction works fine with copper wire, but is not as dramatic because the wire has less surface area.

A smaller version of the demonstration uses a bit of copper, a small volume of nitric acid, and a borosilicate glass test tube.

Perform the Copper and Nitric Acid Chemistry Demonstration

Nothing could be easier! Set up and perform the demonstration inside a fume hood.

Copper and Nitric Acid Reaction

  • Pour the nitric acid into the flask.
  • When you are ready for the reaction, add the copper.

Initially, the nitric acid attacks the copper, turning the liquid green and releasing heat and reddish brown nitrogen dioxide vapor. Eventually, even the liquid turns brown.

  • Add water and dilute the solution.

Diluting the acid changes the conditions. The liquid changes color into a bright blue, while the vapor changes from reddish brown to colorless.

A Look at the Chemistry

If you look at the metal reactivity series, copper is pretty unreactive. It’s even considered a noble metal by some chemists. It resists oxidation by hydrochloric acid (HCl), yet readily reacts with nitric acid (HNO 3 ). This is because nitric acid acts both as an oxidizer and an acid. Copper reacts with nitric acid, forming aqueous copper nitrate, nitrogen dioxide gas, and water.

Cu(s) + 4HNO 3 (aq) → Cu(NO 3 ) 2 (aq) + 2NO 2 (g) + 2H 2 O(l)

The reaction immediately produces heat (reaching 60 to 70 degrees C) and releases deeply-colored nitrogen dioxide gas. The green color comes from copper(II) ions forming a coordination complex with nitrate ions. Diluting the concentrated acid with water changes the liquid color to blue as the water displaces the nitrate ions, leaving only aqueous copper(II) nitrate. The water reacts with nitrogen dioxide and forms nitric oxide.

3Cu(s) + 8HNO 3 (aq) → 3Cu 2+ (aq) + 2NO(g) + 4H 2 O(l)+ 6NO 3 − (aq)

The concentration of the acid affects its oxidizing capacity. For example, copper does not react with dilute sulfuric acid (H 2 SO 4 ), but a similar reaction occurs in concentrated sulfuric acid:

Cu + 2H 2 SO 4  → SO 2  + 2H 2 O + SO 4 2−  + Cu 2+

Containing the Copper and Nitric Acid Reaction

A few simple revisions contain the reaction and improve both the safety and dramatic effect of the copper and nitric acid chemistry demonstration. You can perform this variation of the copper and nitric acid reaction out in the open, but it’s still a good idea to separate the set-up from the audience using a safety shield.

  • Add nitric acid to a round-bottomed borosilicate flask. Clamp it into position on a stand. Ideally, use a borosilicate flask and place a bowl beneath the flask in case the glass leaks or breaks.
  • Fill an Erlenmeyer (conical) flask with water and clamp it into position near the round flask.
  • Stopper the round flask (acid) and loosely plug the conical flask with glass wool. The glass wool prevents the escape of nitrogen dioxide into the outside air. Insert glass tubing the ends reach the bottoms of each flask. (Don’t use plastic tubing.)
  • When you are ready for the demonstration, add the copper to the borosilicate flask and fit the stopper and tube onto it.

Initially, the liquid in the round flask turns green and evolves reddish brown nitrogen dioxide. After about a minute and a half, the reaction slows and cools. The pressure reduction from the cooling draws water in from the conical flask. This dilutes the nitric acid and also reacts with the nitrogen dioxide gas, forming a fountain. Finally, the liquid in the round flask turns blue as copper nitrate forms.

Safety and Disposal

  • Only perform this demonstration if you are a chemist or chemistry educator and have access to proper safety gear and a fume hood. Nitric acid is a corrosive strong acid, while nitrogen dioxide is a toxic reddish-brown gas. Wear gloves, goggles, and a lab coat. Perform the open demonstration under a fume hood.
  • Please choose sturdy glassware for this demonstration. The initial reaction produces heat, so there is a risk of glassware breakage. For this reason, a boiling flask is ideal. Alternatively, use a Buchner flask.
  • After the demonstration, neutralize the dilute nitric acid using any inorganic base, such a baking soda, sodium hydroxide solution, or potassium hydroxide solution. The neutralization reaction also produces some heat. Afterward, you can safely wash the liquids down the drain with water.
  • Cotton, F. Albert; Wilkinson, Geoffrey (1988). Advanced Inorganic Chemistry (5th ed.). New York: John Wiley & Sons. 769-881.
  • Shakhashiri, Bassam Z. (1985). “Properties of Nitrogen(II) Oxide”. Chemical Demonstrations: A Handbook for Teachers of Chemistry Volume 2 . The University of Wisconsin Press. ISBN: 978-0299101305.
  • Shakhashiri, Bassam Z. (1985). “Coin-Operated Red, White, and Blue Demonstration: Fountain Effect With Nitric Acid and Copper”. Chemical Demonstrations: A Handbook for Teachers of Chemistry Volume 3 . The University of Wisconsin Press. 83-91. ISBN: 978-0299119508.
  • Summerlin, Lee R.; Borgford, Christie L., Ealy, Julie B. (1988 ). Chemical Demonstrations: A Sourcebook for Teachers Volume 2 (2nd ed.). American Chemical Society. ISBN: 978-0841215351.

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COMMENTS

  1. Copper and Nitric Acid Chemistry Demonstration

    The copper and nitric acid reaction is a dramatic color change chemistry demonstration. The reaction illustrates several chemistry principles, including exothermic reactions , redox reactions , coordination complexes, oxidation, oxidation states , and the metal activity series .

  2. Reaction of copper with nitric acid - YouTube

    Declan Fleming shows how copper can in fact react with some acids by demonstrating the reaction of copper and nitric acid, producing a visually stunning reaction.

  3. Dissolving copper in nitric acid | Exhibition chemistry | RSC ...

    As well as showing how dramatically copper reacts with nitric acid, this adapted demonstration also uses the high solubility of nitrogen dioxide to initiate a pleasing fountain. Source: Declan Fleming

  4. Reactions of metals with acids producing salts | Experiment ...

    Lesson 1 is a series of test tube experiments in which each working group establishes as a common feature that hydrogen is given off as metals react with an acid – if the metal reacts at all. This should take around 40 minutes, and most classes should be able to do this version.

  5. Copper and Nitric Acid Reaction | Cu + HNO3

    Dilute nitric acid reacts with copper and produce copper nitrate ( Cu (NO 3) 2 ), nitric oxide (NO) and water as products. In this reaction, copper is oxidized while nitric acid is reduced to nitric oxide. After the reaction, solution which contains Cu (NO 3) 2 is blue color. Balanced equation.

  6. Experiment 11 – A Cycle of Copper Reactions - Laney College

    Experiment 11 – A Cycle of Copper Reactions. In this experiment, you will perform and observe several reactions of copper. This is a cycle of reactions, because you start and end with the same substance, copper metal. In the first reaction, copper metal is oxidized by nitric acid to form copper (II) nitrate, Cu(NO3)2.

  7. The determination of copper in brass | Experiment - RSC Education

    In this experiment, students determine the copper content in brass (an alloy of copper and zinc) by dissolving brass turnings in nitric acid and comparing the colour of the solution with that of solutions of various concentrations of copper. It should take approximately 25 minutes.

  8. Copper Metal in Nitric Acid - YouTube

    eCHEM 1A: Online General ChemistryCollege of Chemistry, University of California, Berkeleyhttp://chemistry.berkeley.edu/echem1aCurriculum and ChemQuizzes dev...

  9. Reactions of Cu - umb.edu

    EXPERIMENT. Reaction of Metallic Copper with Nitric Acid Solution. Obtain a piece of copper wire and measure its mass on an analytical balance. Record the mass on the proper line on the top of page 8. Roll the wire into a flat coil and place it in a clean 150-mL beaker labeled with your initials.

  10. Reactions of Copper Experiment - Cerritos College

    In this experiment you will observe a sequence of copper reactions. The sequence begins with copper metal and ends with copper metal, so it is called a cycle of copper reactions. Observations will be made for each reaction. Since no copper is added or removed between the initial and final reaction steps, copper can be quantitatively recovered.