$\require{mhchem}$

Black silver oxide is heated in a test tube to give metallic silver and oxygen gas. The gas is captured in a balloon.

Curriculum Notes 

This demo can be used at the beginning of the general chemistry sequence to illustrate the process of the discovery of chemical elements. It can also be used to demonstrate a decomposition reaction, a redox reaction, or the metal reactivity series. This demo takes about 10 minutes to perform.

One day of lead time is required for this project.

Discussion 

Lavoisier's decomposition of mercuric oxide was a revolutionary experiment in the history of chemistry, but most instructors are reluctant to reproduce it in the classroom due to the toxicity of mercury and its compounds. This demo parallels Lavoisier's experiment closely. The product, though not as cool as mercury, is still very pretty and most students are familiar with the appearance of silver.

$\ce{2Ag2O(s) -> 4Ag(s) + O2(g)  }$

Materials 

• 5g Ag₂O in a 175X25mm test tube w/lip (not a culture tube).
• balloon
• test tube clamp
• alcohol burner
• lighter
• 125mL Erlenmeyer flask

Procedure 

• Stretch the balloon over the mouth of the test tube.
• Heat the bottom of the test tube directly in the hottest part of the flame of the alcohol burner.
• After a couple of minutes, the silver oxide will begin to turn silver and the balloon will inflate slightly.
• Continue heating until all of the silver oxide has decomposed.
• Set the test tube in the flask to cool.

Safety Precautions 

• Silver oxide is a strong oxidizer. Handle with care. Do not leave in contact with combustible materials.
• Keep a fire extinguisher at hand. Clear area of combustible materials.