Chapter 8, Problem 8.39E

Colorless ${\text{N}}_2{\text{O}}_4$ gas decomposes to form red-brown colored ${\text{NO}}_{\text{2}}$ gas. Describe how the concentrations of ${\text{N}}_2{\text{O}}_4$ and ${\text{NO}}_{\text{2}}$ would change (increase or decrease) as equilibrium was established in a sealed container that initially contained only ${\text{N}}_{\text{2}}{\text{O}}_{\text{4}}$. What observation would indicate that equilibrium had been established?