An Overview of the Equilibrium Constant

In a chemical reaction, the equilibrium constant is the value of the reaction quotient at chemical equilibrium, which is a condition attained by a dynamic chemical system after a significant amount of time has elapsed and at which its composition shows no discernible propensity to change in the future.

Depending on the reaction circumstances used, the equilibrium constant can be calculated regardless of how high the initial analytical concentrations of the reactant and product species are in the combination.

The composition of a system at equilibrium can be determined from the initial composition of the system by using established equilibrium constant values. 

However, reaction characteristics such as temperature, solvent, and ionic strength can all have an impact on the value of the equilibrium constant in a chemical reaction system.

Many chemical systems, as well as biological processes such as oxygen transport by haemoglobin in blood and acid–base balance in the human body, can only be understood with a thorough grasp of equilibrium constants.

Equilibrium constants include stability constants, formation constants, binding constants, association constants, and dissociation constants, to name a few different types.

Definition of The Equilibrium Constant 

The equilibrium constant for a chemical reaction can be stated as the ratio between the amount of reactant and the amount of product, and it is used to determine the chemical behaviour of the reaction by determining the quantity of reactant and the amount of product.

Whenever a chemical reaction reaches equilibrium, the balance constant (commonly denoted by the symbol K) provides information about how well a reaction is working and how well it is working well.

Rate of forward and backward reaction is the same. 

Relationship between forward and backward reaction is constant at a given temperature and is called equilibrium constant (K_equ).

Formula for The Equilibrium Constant

K_equ= k_f/k_b = {[C]c [D]d} / { [A]a [B]b = Kc}

K_c is the equilibrium constant.

For gaseous reaction formula will be:-

Kequ = k_f/k_b = { [pC]c [pD]d }\ { [pA]a [pB]b }= Kp

When expressed in terms of partial pressures, K_p denotes the equilibrium constant formula in terms of partial pressures.

Higher K_c/K_p values suggest greater product creation as well as higher percentage conversion rates.

Product formation and conversion are lower when the K_c/K_p values are lower,

K_c/K_p levels in the middle range imply optimal product formation.

Equilibrium Constant Conditions

The equilibrium constant does not depend on any analytical concentration of any product or reactant in a mixture, but it does depend on the ionic strength of the reactants and products, as well as the temperature at which the solution is maintained when a chemical reaction occurs. 

The following are two critical considerations to keep in mind:

When the chemical reaction equation is balanced, the system is in equilibrium; otherwise, the system is out of equilibrium.

In addition, the pressure and concentration of the reactants and products in a solution should be kept in equilibrium as much as possible.

Various factors, such as concentration, pressure, and temperature, all influence the equilibrium position of a reaction, and a catalyst has an impact on the rate of a reaction.

The Equilibrium Constant’s Characteristics

Because it is reaction-specific, and because it is stable at a constant temperature,

A catalyst alters the rate of both forward and backward reactions in the same way, but does not change the value of the equilibrium constant in any way.

Changes in concentration, pressure, temperature, and inert gases can all have an effect on the equilibrium, favouring either the forward or backward response, but not the equilibrium constant, which is constant regardless of the changes.

K_equ has variable values depending on the temperature of a reversible reaction for the same reaction.

It is the reciprocal of the original equilibrium constant, i.e. K_rev = 1/K_equ,that determines the equilibrium constant of the reverse equilibrium (or vice versa).

When the stoichiometry of the equilibrium reaction is modified, the power of the equilibrium constant is likewise changed by the same amount.

Applications of  Equilibrium Constant 

The Equilibrium Constant Is Used to Predict the Extent of the Reaction.

Using the equilibrium constant (Kc), it is possible to anticipate the extent of a reaction, which is the degree to which the reactants vanish into solution.

We can estimate the relative amounts of reactants and products present in the system based on the size of the equilibrium constant.

When the equilibrium constant is more than 103, it indicates that the forward reaction is favoured, which means that the concentration of products is significantly greater than the concentration of reactants at equilibrium.

As an illustration:

H₂(g) + Br₂(g)⇌ 2HBr(g) ⇒ Kc = 5.4×10¹⁸

This demonstrates that the concentration of the products is extremely high at equilibrium, indicating that the reactions are almost complete.

Conclusion

The equilibrium constant is defined as the ratio of the concentrations of products to the concentrations of reactants in a reaction. 

When a chemical reaction reaches equilibrium, the equilibrium constant may be calculated for that particular reaction. 

Following the achievement of this goal, the concentrations of each and every molecule participating in the process are determined.

Because the chemical reaction took place in an equilibrium state, the equilibrium constant does not vary for a given reaction when it takes place in equilibrium.