The key difference between chemical equilibrium and dynamic equilibrium is that the chemical equilibrium describes the state at which concentrations of reactants and products do not undergo any change whereas the dynamic equilibrium describes the state at which ratio of reactants and products do not change, but substances move between the chemicals at an equal rate.
When one or more reactants get converted to products, they may go through different modifications and energy changes. The chemical bonds in the reactants are breaking, and new bonds are forming to generate products, which are totally different from the reactants. We name this kind of chemical modification as a chemical reaction. Thermodynamics is the study of transformations of energy that concerns with the energetic and the position of the equilibrium in a reaction.
CONTENTS
1. Overview and Key Difference
2. What is Chemical Equilibrium
3. What is Dynamic Equilibrium
4. Side by Side Comparison – Chemical Equilibrium vs Dynamic Equilibrium in Tabular Form
6. Summary
What is Chemical Equilibrium?
Chemical equilibrium is the state in which both reactants and products are present in concentrations which have no further tendency to change with time. Some reactions are reversible, and some reactions are irreversible. In a reaction, reactants are converting to products. And in some reactions, the reactants generate again from the products. Hence, this type of reaction is reversible.
In irreversible reactions, once the reactants are converted to products, they do not regenerate again from the products. In a reversible reaction when reactants are going to products, we call it the forward reaction, and when products are going to reactants, it is the backward reaction.
Figure 01: Amount of Reactants (in red) decrease and Amount of Products (in blue) increase after the Chemical Equilibrium
Nature of the Reaction
When the rate of forward and backward reactions is equal, then the reaction is at equilibrium. Therefore, over some time the amount of reactants and products are not changing. Reversible reactions always tend to come to equilibrium and maintain that equilibrium. When the system is at equilibrium, the amount of products and the reactants are not necessarily equal. There can be a higher amount of reactants than the products or vice versa. The only requirement in an equilibrium equation is to maintain a constant amount from both over time. For a reaction in equilibrium, we can define an equilibrium constant; where it is equal to the ratio between the concentration of products and concentration of reactions.
K= [product]n/[reactant]m
Where, n and m are the stoichiometric coefficients of the product and reactant. For an equilibrium reaction, if the forward reaction is exothermic, then the backward reaction is endothermic and vice versa. Normally, all the other parameters for forward and backward reactions are opposite to each other like this. Therefore, if we want to facilitate either one of the reactions, we simply have to adjust the parameters to facilitate that reaction.
What is Dynamic Equilibrium?
Dynamic equilibrium is also a type of equilibrium where the amounts of products and reactants do not change over time. However, in dynamic equilibrium, by saying that the amounts do not change does not mean that the reaction has stopped. Rather, the reaction is proceeding in a way that it keeps the amounts unchanged (the net change is zero).
Figure 02: Change of Forward and Backward Reactions in a Dynamic Equilibrium
Simply the word “dynamic equilibrium” means that the reaction is reversible and continuing. For a dynamic equilibrium to take place, the system should be a closed one, so that no energy or matter escapes from the system.
What is the Difference Between Chemical Equilibrium and Dynamic Equilibrium?
Dynamic equilibrium is a type of chemical equilibrium. The key difference between chemical equilibrium and dynamic equilibrium is that chemical equilibrium describes the state at which concentrations of reactants and products do not undergo any change, whereas the dynamic equilibrium describes the state at which ratio of reactants and products does not change, but substances move between the chemicals at an equal rate.
Moreover, in a dynamic equilibrium, the reaction continues, but the amount of reactants and products remain unchanged because the rates of the forward and backward reactions are the same. There can be some instances in chemical equilibrium where the amounts of products and reactant remain unchanged because the reaction has stopped. So, this is also a difference between chemical equilibrium and dynamic equilibrium.
Below infographic on the difference between chemical equilibrium and dynamic equilibrium provides more information on these differences.
Summary – Chemical Equilibrium vs Dynamic Equilibrium
An equilibrium is a state of a system which shows no net change. Chemical equilibrium obtains this state when the reaction stops while the dynamic equilibrium obtains this state when the forward and backward reaction rates are equal. The key difference between chemical equilibrium and dynamic equilibrium is that chemical equilibrium describes the state at which concentrations of reactants and products do not undergo any change, whereas the dynamic equilibrium describes the state at which the ratio of reactants and products does not change, but substances move between the chemicals at an equal rate.
Reference:
1. “Chemical Equilibrium – Types ,Principles and Laws of Equilibria.” Toppr Bytes, Toppr.com, 16 Mar. 2018. Available here
“Dynamic Equilibrium.” Wikipedia, Wikimedia Foundation, 17 Dec. 2018. Available here
Image Courtesy:
1.”ChemicalEquilibrium”By Fintelia – Own work, (CC BY-SA 3.0) via Commons Wikimedia
2.”Dynamic equilibrium”By Petergans at English Wikipedia – Own work (Public Domain) via Commons Wikimedia