Chemical Equilibrium: NO2 System

Today we are looking at the reversible reaction of nitrogen dioxide to and from dinitrogen tetraoxide. Here is the reaction equation: 2 NO2 (--) N2O4 + Heat. NO2 is reacting to form N4O4 while N2O4 is reacting to form NO2 again. The forward and reverse reactions are taking place at fixed rates. However, you can change the rate at which the reaction occurs, therefore change the concentration of these two gases. NO2 is brown, N2O4 is colorless. When you heat the system, more of the N2O4 will break down to form NO2, thus turning the system brown. When cooled, the N2O4 cannot break down as much and the system will become light brown, closer to colorless. This is a great way to demonstrate LeChatlier's principle, as a small change in heat visibly alters the concentration of both gases, thus changing the color of the system. I'd highly recommend using this in the classroom as long as you can safely contain this toxic gas. Enjoy!