The Idea of Dynamic Chemical Equilibrium

What would happen if our reaction between H2 and I2 to form HI were able to proceed in both the forward and reverse directions  

Dynamic equilibrium—In a chemical reaction, the condition in which the 

This condition is not static—it is dynamic because the forward and reverse reactions are still occurring but at the same constant rate. When dynamic equilibrium is reached, the concentrations of H2, I2, and HI no longer change. They remain the same because the reactants and products are being depleted at the same rate at which they are being formed. 

Notice that dynamic equilibrium includes the concepts of sameness and constancy that we discussed in Section 15.1. When dynamic equilibrium is reached, the forward reaction rate is the same as the reverse reaction rate (sameness). Because the reaction rates are the same, the concentrations of the reactants and products no longer change (constancy). However, just because the concentrations of reactants and products no longer change at equilibrium does not imply that the concentrations of reactants and products are equal to one another at equilibrium. Some reactions reach equilibrium only after most of the reactants have formed products. (Recall strong acids from Chapter 14.) Others reach equilibrium when only a small fraction of the reactants have formed products. (Recall weak acids from Chapter 14.) It depends on the reaction. 

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