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The NO/CS2 Cannon

Chemical Concepts Demonstrated

  • Complex stoichiometry
  • Exothermicity

Demonstration

  • A tube filled with NO gas is sealed with a rubber stopper.
  • CS2 is quickly added to the tube (the demonstrator is careful not to allow any air to be admitted, since NO reacts with oxygen to form NO2).
  • The tube is inverted to insure complete mixing.
  • The rubber stopper is then removed, and a lighted match is thrown down the tube.
cannon.gif

Observations

As the match travels down the tube, a massive flame and a loud roar shoot forth from the top of the tube.

Explanation (include important chemical equations)

The reaction witnessed involves a very complex stoichiometry:

5 CS+ 10.8 NO -> 5.4 N+ 2.6 CO + 2.4 CO+1.7 SO+ 8.3 S

The reaction is first-order in CSand second-order in NO.  The activation energy is 300 kJ/mol, which is the energy required to remove an S from CS2.  The energy released in this reaction is a whopping 3,280 kJ/mol.

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