16.4 The NO/CS2 Cannon

Chemical Concepts Demonstrated: Complex stoichiometry, exothermicity


  • 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.


    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 CS2 + 10.8 NO -> 5.4 N2 + 2.6 CO + 2.4 CO2 +1.7 SO2 + 8.3 S

    The reaction is first-order in CS2 and 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.