When a chemical system is in a state where the concentration of the chemical reactants and the concentration of the products formed undergo no changes over time, the chemical system is said to be in a state of chemical equilibrium. At a point of chemical equilibrium, the rate of the forward reaction is said to be equal to the rate of backward reaction. This article aims to explain the concept of chemical equilibrium and the various factors that affect it.
An Introduction to Chemical Equilibrium
Chemical equilibrium is known to be affected by several factors such as changes in the concentration of either reactants or products, the common ion effect, changes in the temperature of the reaction environment, or the introduction of a chemical catalyst. But what exactly is chemical equilibrium? Consider the following chemical equation:
A + B → C + D
Here, the reactants A and B participate in a chemical reaction with each other to afford the products C and D respectively. However, the following chemical equation occurring in the same chemical system can be considered:
C + D → A + B
Here, the products C and D react with each other to regenerate the reactants A and B respectively. Therefore, there are two different reactions occurring simultaneously in this chemical system. The first reaction is between the reactants A and B (which yields products C and D). The second reaction is between the products C and D (which yields reactants A and B). If the rate of the first reaction is equal to the rate of the second reaction, then the system can be represented via the following chemical equation:
A + B ⇌ C + D
This equation suggests that a chemical equilibrium exists between the reactants (A and B) and the products (C and D). The next subsection will cover the different factors that affect such a chemical equilibrium.
Factors that Affect Chemical Equilibrium
Increasing the Concentration of the Reactants/Products
If the concentration of the reactants is increased, the chemical equilibrium will shift in the direction where a larger amount of the substance with increased concentration is consumed. The same principle applies when the concentration of the products is increased as well. For example, if the concentration of the reactants A and B in the previous reaction is increased by 1 mole each, then there will be an increase in the concentration of C and D as well. Follow the hyperlink to learn about the concept of mole chemistry.
Increasing the Temperature of the Reaction Environment
Increasing the temperature of the reaction environment for a chemical system in a state of chemical equilibrium will have varying effects based on the nature of the reaction. If the chemical reaction is an exothermic reaction, then increasing the temperature will increase the concentration of the reactants. However, if the reaction is an endothermic reaction, then increasing the temperature will increase the concentration of the products that are formed in the chemical reaction.