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The situation or condition in a reversible reaction wherein zero net change in the number of reactants and products takes place is known as a chemical equilibrium. At equilibrium state, the two opposite reactions occur at equal rates or velocities, and therefore one can observe the negligible net change in the amounts of those substances which are involved. In this situation, one may also say the reaction has been completed.
In simple words, chemical equilibrium can be explained as the condition in which there is an equilibrium in the chemical process. It is that state in a chemical reaction in which the concentration of the reactant, as well as that of the product, stays constant over some time and the system’s properties also remain the same. It can be said that the system reaches a chemical reaction as and when the rate of the forward reaction is equal to the rate of the reverse reaction.
Reactants and Products
For gaining a proper understanding of equilibrium in a chemical reaction, it is crucial to also understand what are reactants and what are products. Reactants can be explained as those substances which are useful for initiating a chemical reaction. On the other hand, products are called those substances which are formed once the chemical reaction has been completed.
Types of equilibrium
There are mainly two types of equilibrium, each one unique from the other. These include:
- Homogeneous equilibrium – Homogeneous equilibrium can be explained as the type of equilibrium in which the state of reactants and products is the same. Such that, if the reactants are in a gaseous state then the products would also be in a gaseous state. Similarly, for liquid and solid-state as well.
For example,
N2(g) + 3H2(g) ⇌ 2NH3(g)
In the above reaction, it can be observed that the products, as well as reactants, are in a gaseous state therefore it is homogeneous equilibrium.
- Heterogeneous equilibrium – Heterogeneous equilibrium can be understood as the state of equilibrium wherein the state of reactants is different from the state of products. For example, if the reactants are in the gaseous state then the products can be in some state other than gaseous. To explain it through the equation, please see below:
H2O(l) ⇌ H2O(g)
In the above reaction, H2O is converted from a liquid state to a gaseous state, therefore this reaction can come under the heading of heterogeneous equilibrium.
Factors impacting equilibrium
Equilibrium can get impacted because of various different factors such as concentration, pressure and temperature. Using Le Chatelier’s principle, the effect of these phenomena can be easily understood on equilibrium. According to Le Chatelier’s principle, concentration can impact equilibrium such that if a reactant or product is added then the chemical reaction proceeds in the same direction in which the reactant or product gets consumed. Further, if the reactant or product is removed then reaction proceeds in the direction wherein the removed reactant or product will be replenished. Pressure change does not impact equilibrium in the case of solid as well as liquid; however, in gas if the pressure has increased then the direction of reaction becomes opposite and equilibrium shifts in the backward direction. Lastly, for temperature, when it is an exothermic reaction then the equilibrium constant gets reduced as the temperature is increased. In the case of an endothermic reaction, an increase in equilibrium constant can be observed as temperature increases.
Conclusion
As observed from the above discussion, it can be concluded that the process of chemical equilibrium involves the condition in which there is an equilibrium in the chemical process. A chemical equation has reactants as well as products. Reactants refer to the substances which are useful for initiating a chemical reaction. On the other hand, products are known as those substances which are formed once the chemical reaction has been completed. There are broadly two types of chemical equilibrium, homogeneous equilibrium and heterogeneous equilibrium. Both the processes have unique properties that differentiate them from one another. The process of equilibrium can get impacted due to a lot of factors such as pressure, temperature and concentration.
