Explain observable properties and the characteristics of physical and chemical systems in a state of equilibrium.

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: \[2\text{NO}_2(g) \rightleftharpoons \text{N}_2\text{O}_4(g)\] Nitrogen dioxide is a brown gas, while dinitrogen tetroxide is colourless. Once equilibrium is established in the flask, the colour of the gas mixture remains constant over time. Explain why the colour of the gas mixture does not change once equilibrium is established.

A colourless solution of nitrogen dioxide, \( \text{N}_2\text{O}_4(\text{g}) \), is sealed in a rigid container and allowed to decompose according to the equation: \[ \text{N}_2\text{O}_4(\text{g}) \rightleftharpoons 2\text{NO}_2(\text{g}) \] where \( \text{NO}_2(\text{g}) \) is a brown gas. After some time, the system reaches dynamic equilibrium and the solution appears light brown. Which of the following best explains why the colour remains constant once equilibrium is established?

Which of the following best explains why the mass of a sealed container remains constant when the reversible reaction \(\text{N}_2\text{O}_4(g) \rightleftharpoons 2\text{NO}_2(g)\) reaches equilibrium?