Examples: Equilibrium

Introduction

In this article, you will learn all the important concepts related to the alternation of generation. We have introduced the concept of chemical equilibrium from Chapter 7: Equilibrium from CBSE Class 11th Chemistry. We will discuss the concepts of equilibrium, equilibrium reaction, chemical equilibrium, chemical equilibrium examples, classification of chemical equilibrium, and the types of equilibrium.

Equilibrium is an important topic in chemistry, and chemical equilibrium is a topic that requires it to be understood deeply with full concentration.

Let us start by defining equilibrium.

What is Equilibrium?

Equilibrium is a state in chemistry in which there is no net change in the concentrations of the products as well as the reactants.

In other words, equilibrium is a state of the body where neither the inner energy nor the movement of the body shifts with time. It is the point when the net superficial force and the torque working on the body about the COM or any other point are zero.

Equilibrium is categorised as unstable, stable, and neutral equilibrium.

Stable equilibrium: An example of stable equilibrium is a ball kept at the bottom of a hemisphere.

Unstable equilibrium: If we consider a ball kept on top of a sphere, it is an example of unstable equilibrium. The ball will roll away from the topmost point if we slide it.

Neutral equilibrium: This refers to the state when the body does not move towards or away from the equilibrium point.

What is an Equilibrium reaction?

An equilibrium reaction refers to the chemical reaction between the reactants before and after the reaction is complete (i.e., a thermodynamic equilibrium state). An example of an equilibrium reaction is water evaporating to form vapour.

A thermodynamic equilibrium state refers to a reaction that satisfies all types of equilibrium. These are as follows:

• Thermal equilibrium
• Chemical equilibrium
• Mechanical equilibrium

Chemical Equilibrium

Chemical equilibrium is the state of a system where the concentration of the product and the reactant do not alter with time or show any additional changes in their properties.

Classifications of Chemical Equilibrium

There are two categories of chemical equilibrium:

1. Homogeneous equilibrium
2. Heterogeneous equilibrium

Homogeneous Equilibrium

When all the products and reactants of the chemical equilibrium are in a similar phase, it is known as homogeneous equilibrium. Moreover, there are two types of homogeneous equilibrium:

1. Reactions in which the amount of molecules in the reactants is equal to the number of molecules in the products. For example: O2 (g) + N2 (g) ⇌ 2NO (g)
2. Reactions in which the total amount of reactant molecules is not equal to the number of molecules in the products. For example: Cl2 (g) + CO (g) ⇌ COCl2(g)

Heterogeneous Equilibrium

When the products and reactants of chemical equilibrium are present in different phases, it is known as heterogeneous equilibrium. For example:  

CO2 (g) +  CaO (s)⇌CaCO3 (s)

Hence, the various types of chemical equilibrium are based on the phases of the products and the reactants.

Factors Affecting Chemical Equilibrium

There are various factors such as the pressure, concentration, and temperature of the system that affect chemical equilibrium. Some important factors that affect chemical equilibrium are as follows:

Change in Concentration:

• The concentration of the products or reactants added is ridden by the reaction which absorbs the substance which is added.
• The concentration of the products or reactants eliminated is reduced by the reaction that is in the direction of restoring the substance that is removed.
• When the concentration of the products or reactants is altered, there is a modification in the composition of the combination in the chemical equilibrium.

Change in Pressure:

A change in pressure occurs due to modification in the volume. A change in the pressure can influence the gaseous reaction since the total quantity of the gaseous products and reactants become varied.

Change in Temperature:

The impact of temperature on chemical equilibrium relies upon the sign of ΔH of the reaction and follows Le-Chatelier’s principle.

• As the temperature boosts, the equilibrium constant of an exothermic reaction lessens.
• The equilibrium constant rises with a rise in temperature in an endothermic reaction.

Effect of a Catalyst:

A catalyst only speeds up a reaction and does not influence the chemical equilibrium. It equally speeds up both the reverse and the forward reactions. This influences the reaction to attain its equilibrium faster.

The same number of products and reactants are present at equilibrium in a catalysed and uncatalysed reaction. The presence of a catalyst only stimulates the reaction to proceed through a low-energy transition state of reactants to products.

Effect of Addition of a Non-reactive Gas:

When a non-reactive gas like argon is added to a constant quantity, it does not take part in the reaction and so the equilibrium remains undisturbed. If the gas added is a reactant or a product included in the reaction, then the reaction quotient will be altered.

Chemical Equilibrium Examples

In a chemical reaction, the reactants are changed into the products. After the reaction starts, the rate of the backward and forward reactions may be similar. Then, the reactants that were converted are again made by the reverse reaction. As a result, the products and the reactants are in chemical equilibrium.

• H2 + N2 ⇌ 2NH3
• PCl2 + PCl3 ⇌ PCl5
• 2NO2 ⇌ N2O4

Conclusion

In this article, we have discussed the concept of equilibrium and equilibrium reactions as well as their classifications. We learned that equilibrium refers to a state in chemistry that shows no net change in the concentrations of the products or the reactants. Moreover, an equilibrium reaction is a chemical reaction between the reactants before and after the reaction is complete (i.e., a thermodynamic equilibrium state). An equilibrium reaction example is water evaporating to form vapour. We also discussed the concept of chemical equilibrium and the factors that affect chemical equilibrium.