Nitrogen Dioxide and Dinitrogen Tetraoxide

The two substances in this reaction are NO2 and N2O4. This reaction is a reversible reaction, which is how it reaches equilibrium.takes more energy. These two are the main components in smog, and the formation of N2O4 reaction  The whole reaction is 2NO2 --> N2O4 with an enthalpy of -58.0 kJ/mol of N2O4

 The reaction is temperature favored. The cold ice water favors the N2O4, therefore changing the rate of the production of N2O4 and  boosting the molarity of it. The heat from the bunsen burner favors the NO2 side of the reaction, making the rate of NO2 faster than the rate of N2O4.

You can tell the cold favors the N2O4 because N2O4 is naturally a clear gas. But as soon as you move the test tube into the boiling water the gas turns a yellowish brown color, showing that the reaction has reversed and the NO2 is more favored because NO2 in gas form is that color. the NO2, when placed in the boiling water, pops. This is due to the greater number in moles. Le Chatelier's principle can be used to predict the effect of the change of conditions in an equilibrium reaction. The equilibrium shift has to do with enthalpy of the reaction. One side if the reaction favors the release of energy, and one favors the absorption if energy. The color change has to do with the equilibrium trying the compensate for the change that the rate of the reaction is kept the same. The reaction at room temperature is a equal mixture of both NO2 and N2O4 color with neither one favored more than the other, compared to the favoring of the reaction side depending on the temperature.