Final answer:
True, water vapor can reach an equilibrium state in a decomposition or phase change process, resulting in a constant vapor pressure and a dynamic equilibrium where vaporization and condensation rates are equal.
Step-by-step explanation:
The student asked whether it is true or false that in the decomposition of water vapor, equilibrium is established. The answer to this is true. When water vapor decomposes into its constituent elements, the system can indeed reach a state of equilibrium. Similarly, the rate at which water molecules turn from the liquid to the gas increases and eventually equals the rate of gas molecules entering back into the liquid, leading to a state where the vapor pressure of the gas is constant, a situation often referred to as dynamic equilibrium. Dynamic equilibrium means that the forward and reverse reactions are happening at the same rate, so while there is always constant activity, no net change occurs in the concentrations of the reactants and products. This concept is a fundamental aspect of chemical systems and can be observed in closed systems where condensation and vaporization of water occur.