Keywords
hydrogen, oxygen, water, energy
Summary
A pop bottle is filled with a 1:2 mixture of oxygen and hydrogen. The Bunsen burner provides the initiation of the combustion reaction, and a loud pop is observed.
Hazards
- It is important to use a thick walled vessel for this procedure. Use only the green "pop bottle" from the demonstration laboratory.
- Hydrogen gas is very flammable.
- Oxygen is an oxidizer.
Chemicals and Solutions
- Hydrogen tank
- Oxygen tank
Materials
- Rubber hose
- Trough
- Coke bottle (Old glass, thick walled)
- #2 solid rubber stopper
- Bunsen burner
- Matches
- Heavy gloves and goggles
- (2L beaker)
Procedure
- Before class, fill the coke bottle and trough with water. Displace 2/3 of the water with H₂ and the remaining 1/3 of the bottle with O₂.
- In the classroom, set-up burner and matches in lecture room.
- To set off the pop bottle, wear goggles and gloves, uncork the bottle and bring the bottle opening horizontally to the burner. BOOM!!!
Hints: If preparing the demo in advance, cork bottle tightly with rubber stopper and invert the bottle in a beaker of water until classtime.
Discussion
\( \ce{ 2H2_{(g)} + O2_{(g)} -> 2H2O_{(g)} ~~~~ \Delta G^{{o}}_{Rxn} = -457.2KJ/Mol } \)
Water is very stable! Once heat provides the necessary activation energy, Ea , the reaction proceeds rapidly. The initial heat and the energy released by the reaction expand the gases greatly, creating an explosive force within the confined space of the bottle.