Final answer:
The balanced equation for hydrogen gas reacting with iodine to form hydrogen iodide is H2(g) + I2(g) → 2 HI(g), which represents a chemical equilibrium.
Step-by-step explanation:
The balanced chemical equation for the reaction between hydrogen gas (H2(g)) and iodine solid (I2(g)) to form hydrogen iodide is given by:
H2(g) + I2(g) → 2 HI(g)
This reaction reaches a dynamic state where the rate of the forward reaction, the combination of hydrogen and iodine, is equal to the rate of the reverse reaction, the decomposition of hydrogen iodide. This state is known as chemical equilibrium. The double arrow (→) in the equation denotes this equilibrium, indicating that both the forward and reverse reactions are occurring simultaneously.