Final answer:
A balanced chemical equation for the formation of hydrogen iodide (HI) is H₂(g) + I₂(s) ⇌ 2HI(g), indicating a reversible reaction between hydrogen gas and solid iodine to form gaseous HI, which can reach a state of chemical equilibrium.
Step-by-step explanation:
To demonstrate the definition with a chemical equation for the formation of hydrogen iodide (HI), consider the reaction between hydrogen gas (H₂) and iodine (I₂). Including phases, the balanced chemical equation is:
H₂(g) + I₂(s) ⇌ 2HI(g)
This equation shows the combination of hydrogen gas and solid iodine forming gaseous hydrogen iodide (HI). The reaction is reversible, represented by the double arrow (⇌), indicating that it can proceed in both the forward and backward directions. This state is known as chemical equilibrium, where the concentrations of reactants and products remain constant over time. Phases are denoted by (g) for gas, (s) for solid, and can also include (l) for liquid and (aq) for aqueous solutions.