RHYS LEWIS & MINH TAN PHAM, AHS, DECD, UNISA / SCIENCE PHOTO LIBRARY RHYS LEWIS & MINH TAN PHAM, AHS, DECD, UNISA / SCIENCE PHOTO LIBRARY
NO2-N2O4 equilibrium. Demonstration of the effect of pressure on the equilibrium between nitrogen dioxide (NO2) and dinitrogen tetroxide (N2O4). The syringe is filled with a mixture of the two gases. NO2 is a brown gas, while N2O4 is colourless. Pressing down on the plunger reduces the volume of the gas and increases its pressure. This leads to a colour change as the equilibrium shifts. First, the mixture darkens as the concentration increases, but then as the equilibrium responds to the increase in pressure it becomes paler. This is because nitrogen dioxide is converted into dinitrogen tetroxide. As the plunger is released the changes reverse.
Model release not required. Property release not required.