In many chemical reactions, both directions are possible; when they are happening at the same rate, that is called dynamic equilibrium, which means "moving equilibrium", because the individual molecul...In many chemical reactions, both directions are possible; when they are happening at the same rate, that is called dynamic equilibrium, which means "moving equilibrium", because the individual molecules are moving back and forth between "reactant" and "product" (which are really just defined by how you write the equation), but the total amounts of reactant and product aren't changing.