For a reaction to be classified as reversible, where must it occur?

A reversible reaction is one in which the products can react to form the original reactants, allowing the reaction to proceed in both the forward and reverse directions. For this to happen effectively, the reaction must take place in a closed system. In a closed system, no reactants or products can escape; therefore, the concentrations of all species involved can reach a state of dynamic equilibrium.

This dynamic equilibrium allows for the ongoing processes of the forward and reverse reactions to occur simultaneously. If the system were open, reactants or products could escape, leading to a shift in concentration that would prevent the establishment of this equilibrium. Thus, a closed system is essential for the characteristics and behavior of reversible reactions to be fully realized.