Explain that, over time, physical change and reversible chemical reactions reach a state of dynamic equilibrium in a closed system, with the relative concentrations of products and reactants defining the position of equilibrium.

A sealed flask contains nitrogen dioxide gas \(\text{NO}_2(g)\) which partially converts to dinitrogen tetroxide \(\text{N}_2\text{O}_4(g)\) according to the equation: \[2\text{NO}_2(g) \rightleftharpoons \text{N}_2\text{O}_4(g)\] After several hours, the brown colour of the gas mixture becomes constant. Which of the following best explains why the colour remains constant?

A sealed flask contains nitrogen dioxide gas \((\text{NO}_2)\), which exists in equilibrium with dinitrogen tetroxide \((\text{N}_2\text{O}_4)\) according to the equation: \[2\text{NO}_2(g) \rightleftharpoons \text{N}_2\text{O}_4(g)\] After the system reaches equilibrium at constant temperature, the concentration of \(\text{NO}_2\) is measured as \(0.040\,\text{mol}\,\text{L}^{-1}\) and the concentration of \(\text{N}_2\text{O}_4\) is \(0.120\,\text{mol}\,\text{L}^{-1}\). Which statement best explains why these concentrations remain constant at equilibrium?

A sealed container holds nitrogen dioxide gas, \(\text{NO}_2\), which exists in equilibrium with dinitrogen tetroxide gas, \(\text{N}_2\text{O}_4\), according to the equation: \[2\text{NO}_2(g) \rightleftharpoons \text{N}_2\text{O}_4(g)\] Explain why the brown colour of the gas mixture in the sealed container remains constant once equilibrium has been established.