An example of chemical equilibrium is represented by which equation?

Chemical equilibrium occurs in a reversible reaction when the rate of the forward reaction equals the rate of the reverse reaction, leading to constant concentrations of reactants and products over time.

In the reaction represented by the equation where hydrogen gas and iodine gas combine to form hydrogen iodide, both the forward reaction (formation of HI) and the reverse reaction (breaking down of HI into H₂ and I₂) can proceed. This dynamic process establishes an equilibrium state where the amount of reactants and products remains constant, reflecting an ongoing exchange between formation and decomposition.

This characteristic makes the equation a correct representation of chemical equilibrium. The other options, while representing various chemical reactions, do not indicate that the reactions can reach an equilibrium state in the same straightforward manner as found in the hydrogen iodide example, or they might refer to combustion processes that typically go to completion rather than establishing an equilibrium. Thus, the chosen example correctly illustrates the concept of chemical equilibrium.