Difference Between Equilibrium Constant and Equilibrium Position

Key Difference – Equilibrium Constant vs Equilibrium Position
 

Equilibrium constant is the number that gives the relationship between amounts of products and reactants of a reaction mixture at its equilibrium whereas equilibrium position is the moment at which the forward reaction of the equilibrium is equal to the backward reaction. This is the key difference between equilibrium constant and equilibrium position.

An equilibrium is the state of a system where there is a forward and backward reaction at the same time. This means, there are opposing reactions that balance each other. The equilibrium constant gives a quantitative explanation of the equilibrium state of a system whereas equilibrium position explains the equilibrium system qualitatively.

CONTENTS

1. Overview and Key Difference
2. What is Equilibrium Constant
3. What is Equilibrium Position
4. Side by Side Comparison – Equilibrium Constant vs Equilibrium Position in Tabular Form
5. Summary

What is Equilibrium Constant?

The equilibrium constant is the number that gives the relationship between amounts of products and reactant of a reaction mixture at its equilibrium. An equilibrium state of a reaction mixture is the state approached by the system at which no further changes of the reactants or products takes place. The equilibrium constant is the ratio between concentrations of products and the reactants.

The equilibrium constant is independent of the initial concentrations of reactants. The factors that affect the value of the equilibrium constant are temperature, nature of the solvent, the ionic strength of ions in the reaction mixture, etc. The equilibrium constant is denoted by “K”.

Equilibrium Constant Equation

A    +   B         ↔       C

For the above reaction, equilibrium constant can be given as below.

K = [C]/ [A][B]

This is also known as the equilibrium constant of concentrations because the concentrations of reactants and products are used in writing the expression. It is denoted by Kc. If the value of the K is higher than 1, the equilibrium favors the products. But if the value of K is lower than 1, the equilibrium favors reactants. When writing the expression of the equilibrium constant, should consider the stoichiometric values of the equation.

aA    +   bB         ↔       cC

The K of above equation is as follows.

K = [C]^c / [A]^a[B]^b

For the reactions between gaseous compounds, the equilibrium constant is given as the equilibrium constant of pressure. It is denoted by Kp. There, the pressure of gases is considered, and the units of the equilibrium constant are given by the units of pressure.

What is Equilibrium Position?

Equilibrium position is the moment at which the forward reaction of the equilibrium is equal to the backward reaction. There is no observable change in the system at the equilibrium position. No net amount reactants are a loss, or no products are formed. If products are formed, they are converted back into reactants and vice versa.

What is the Difference Between Equilibrium Constant and Equilibrium Position?

Equilibrium Constant vs Equilibrium Position
Equilibrium constant is the number that gives the relationship between amounts of products and reactant of a reaction mixture at its equilibrium.	Equilibrium position is the moment at which the forward reaction of the equilibrium is equal to the backward reaction.
Nature
The equilibrium constant is a number which gives the state of equilibrium.	The equilibrium position is a concept used to explain the state of an equilibrium system.
Effect of External Factors
The value of equilibrium constant is changed when some parameters such as temperature, ionic strength are changed.	The equilibrium position does not change due to any change of the system.

Summary – Equilibrium Constant vs Equilibrium Position

The equilibrium constant is a quantitative explanation of the equilibrium state of a system whereas equilibrium position is the qualitative explanation of an equilibrium system. The difference between equilibrium constant and equilibrium position is that equilibrium constant is the number that gives the relationship between amounts of products and reactant of a reaction mixture at its equilibrium whereas equilibrium position is the moment at which the forward reaction of the equilibrium is equal to the backward reaction.

Reference:

1.Libretexts. “The Equilibrium Constant.” Chemistry LibreTexts, Libretexts, 23 Mar. 2018. Available here  
2.“Equilibrium Constant.” Merriam-Webster, Merriam-Webster. Available here  

Image Courtesy:

1.’Equilibrium’By L’Aquatique – Own work, (Public Domain) via Commons Wikimedia