Final answer:
Equilibrium in a chemical reaction requires a closed system with no changes in reactant or product concentrations, and it is a dynamic process where the rates of forward and reverse reactions are equal.
Step-by-step explanation:
For equilibrium to be possible in a chemical reaction, certain conditions must be met within the reaction vessel. Firstly, the system must be closed, which means no substances can enter or leave the system. This is essential to prevent the constant change of the reactant and product concentrations, which would disrupt equilibrium. Secondly, the reaction must be dynamic, with both the forward and reverse reactions occurring at the same rate; hence, the rates of these reactions must be equal. This does not mean the amounts of reactants and products are equal but rather that the quantities remain constant over time once equilibrium has been established.
In addition to these conditions, any changes to the system, such as the removal of products or the addition of reactants, could shift the equilibrium. For example, changes in pressure or volume can affect gas-phase equilibria by altering the concentrations of the reactants and products. It is, therefore, critical to maintain a steady environment in the reaction vessel to achieve and maintain equilibrium.