Chemiluminescent Ammonia Fountain

Introduction

As ammonia gas dissolves in water, the pressure inside the inverted flask is lowered. This decrease in pressure draws the two solutions into the flask, which react to form a glowing chemiluminescent ammonia fountain.

Concepts

• Chemiluminescence
• Solubility of gases

Materials

Safety Precautions

Ammonia vapor is severely toxic and irritating by inhalation and may be fatal. Use only under a fume hood. Ammonia is also a moderate fire risk. Wear chemical splash goggles, chemical-resistant gloves and a chemical-resistant apron. Please review current Safety Data Sheets for additional safety, handling and disposal information.

Disposal

Please consult your current Flinn Scientific Catalog/Reference Manual for general guidelines and specific procedures, and review all federal, state and local regulations that may apply, before proceeding. The remaining solution may be flushed down the drain with excess water according to Flinn Suggested Disposal Method #26b.

Prelab Preparation

1. In a 1-L Erlenmeyer flask, dissolve 4 g of sodium carbonate in approximately 600 mL of distilled water. Add 0.2 g of luminol, stir to dissolve. Add 24 g of sodium bicarbonate, 0.5 g of ammonium carbonate and 0.4 g of copper(II) sulfate. Stir to dissolve. Dilute to 1000 mL with distilled water. Stir. This is Solution A.
2. In a second 1-L flask, add 25 mL of 6% hydrogen peroxide. Dilute to 1000 mL with distilled water and mix well. This is Solution B.

Procedure

1. Prepare the two-hole rubber stopper with water in the medicine dropper as shown in Figure 1. Use rubber tubing to connect the glass tubing pieces.
   {13049_Procedure_Figure_1}
2. Under an operating fume hood, add a few milliliters of concentrated ammonium hydroxide to the round-bottom flask and place it on a warm hot plate until the liquid evaporates.
3. Stopper and invert the flask. Clamp it to the ring stand as shown in the diagram.
4. Attach the rubber tubing from the flask to the T-shaped tubing connector and from each side of the connector to the two 1-L Erlenmeyer flasks full of solutions.
5. Turn down the lights. The darker the room, the more dramatic the effect.
6. Initiate the reaction by squeezing the medicine dropper and allowing a few drops of water to enter the flask.
7. The partial vacuum produced by the ammonia gas dissolving in the water will draw the solutions up into the round bottom flask. As the two solutions mix, they create a beautiful chemiluminescent effect.

Student Worksheet PDF

13049_Student1.pdf

Answers to Questions

1. Draw a diagram of the set-up for this demonstration. Describe what happened in this demonstration.
   {13049_Procedure_Figure_1}

   Student answers may vary. Several drops of water were squeezed through a medicine dropper into the round-bottom flask. The solutions inside the two Erlenmeyer flask were drawn up into the round-bottom flask, creating a fountain. The fountain glowed.

2. Explain how the fountain effect inside the round-bottom flask occurred.

   The round-bottom flask contained ammonia gas, which is soluble in water. When water was injected into the flask some of the ammonia dissolved, decreasing the pressure inside the flask. The pressure drop caused some of the two solutions into the flask, which lowers the pressure even more. The difference in pressure is great enough to create a fountain effect.

3. Define chemiluminescence. Give an example of chemiluminescence found in nature.

   Chemiluminescence is a process by which energy of a chemical rxn is converted to light energy. An example of this that is found in nature is the firefly.

Discussion

Ammonia fountains dramatically show the solubility of ammonia gas in water. Initially, the flask is full of ammonia gas. When a few drops of water are injected into the system, some of the ammonia dissolves in the water. This lowers the pressure inside the flask, drawing up the two solutions. When the solutions enter the flask, more ammonia gas will dissolve, increasing the pressure difference to such a degree that a fountain effect is created.

Chemiluminescence is a process by which energy of a chemical reaction is converted into light energy. Light is produced when electrons drop from an excited or high energy level to a stable or lower energy level. In chemiluminescence, a reaction produces a molecule that is in an excited state. As the electrons in this molecule return to their ground state, energy is released in the form of light. The reaction of luminol with the other chemicals to create the chemiluminescent effect is shown.

References

Shakhashiri, B. Z. Chemical Demonstrations; University of Wisconsin: Madison, 1985, p 156–167.

Thomas, N. J. Chem. Ed. 1990, 67, 431.