Homogeneous Equilibria

Chemical equilibrium is a state of equilibrium that holds reversible reactions. The rate of forwarding reaction and reverse reaction are equal in a Chemical equilibrium. There are two classes of Equilibrium – homogeneous and heterogeneous equilibrium. In the homogeneous equilibria, the chemical reaction always happens in one phase. An example of homogeneous equilibrium will show that the reactants and their products are found in the same state of matter all the time. Note that the equation will always have reactants on the left and products on the right side. The homogeneous equilibria are considered to be the simpler between two types of equilibriums. We will discuss these equilibria while providing a homogeneous equilibrium example. 

Homogeneous and Heterogeneous Chemical Equilibrium

It is essential to understand that the nature of the homogeneous and heterogeneous equilibrium is entirely different, and so are their calculations. These are two different kinds of reactions. While analysing, we can say that for homogeneous reactions, the components of the reaction are present in the same phase, whereas, in heterogeneous reactions, the components are involved in different phases. In most homogeneous equilibrium examples, you will find that the reactions comprise gaseous or liquid components. An example of homogeneous equilibrium has been provided to make you understand the concept of homogeneous reactions:

 C2H2 (aq) + 2Br2 (aq) ⇌ C2H2Br2 (aq)

Therefore, we can see that all the reactants and products are present within the single solution, which can be ions, molecules, or a combination of both.

However, a singular example of homogeneous equilibria might not be adequate to help you understand the concept of equilibrium.

On the other hand, a heterogeneous equilibrium can be described as a system in which products and reactants are seen in two or more phases, and it may be the combination of gas, liquid, or solid. An example of heterogeneous equilibrium has also been provided for you so that you can recognise the difference between homogeneous and heterogeneous equilibrium:

H2O (s) ⇌ H2O (l)

Examples of Homogeneous Equilibrium 

Even though the reactants and products are always in the same phase in homogeneous equilibria, this reaction can be seen in two different forms:

Reactions with a similar number of molecules of both the reactants and the products. 

For example, 

N2 (g) + O2 (g) = 2NO (g)

The example above shows two molecules of reactants on the left side and two molecules of product on the right side.

Reactions with different numbers of molecules of reactants and products.

For example,

2NO2(g) ⇌ N2O4 (g)

Another example of the second category of homogeneous equilibria can be:

2SO2 (g) + O2 (g) ⇌ 2SO3 (g)

This example can be interesting. It is visible in the example as mentioned above that there are 3 molecules of reactant and 2 molecules of product present.

Calculation of Equilibrium Constant 

The equilibrium constant can be calculated for any homogeneous equilibria reaction. To understand this, we must assume that A, B, C, and X are reactants and products. The constant quantity or coefficient is represented by a, b, c, and x. The equation along with their coefficient would look like the example given below:

aA + bB ⇌ cC + xX

Now, to calculate the equilibrium constant from this reaction equation, the products of the equation will go into the numerator, and the reactants will go into the denominator. Their coefficients will become their exponents, respectively. The given equation can be helpful:

Kc = CcXx / AaBb

This formula can be helpful for students to calculate the equilibrium constant of homogeneous and heterogeneous equilibrium equations.

aA + bB ⇄cC + dD

KC = CCDd/AaBb

Here, KC represents equilibrium constant.

So, CCDd/AaBb = concentration of products/concentration of reactants

Homogeneous Equilibrium Reactions

We have already mentioned in this article that if the reactants and products are in the same phase of an equation and it’s in equilibrium, then the state of the reaction is homogeneous equilibrium. There is also an equilibrium constant called Kc.

There are generally no specific state symbols, but the reaction is considered homogeneous. Now, the question is how the equilibrium constant can be calculated. The reactants and products produce a specific amount of measured equilibrium concentration used to calculate homogeneous equilibria. It is observed that the equilibrium constant generally provides the same value all the time, irrespective of the concentration of reactants and products. Another important part is that the equilibrium value does not change even if the pressure or catalyst changes or is absent.

Equilibrium constants in terms of molar concentration and partial pressure can be used to represent homogeneous equilibrium reactions.

Difference between Kp and Kc

The primary distinction between the two equilibrium constants is that they are applied to different concentrations. The equilibrium constant at partial pressure during a reaction is denoted by the symbol KP. These values can be calculated using the reactant and products and equations and their specific values. It was also possible to derive a relationship between the two equilibrium constants, as shown below:

KP = KC(RT)Δn

Conclusion

If you see an overview of the article, we will discover that the two types of equilibrium are critical parts of the entire chemical equilibrium chapter. The equilibrium is constant, and it is represented as KC. Note that the main difference between homogeneous and heterogeneous equilibrium is that the molecules and the state of the equilibrium are different in both reactions. In the homogeneous equilibrium, substances are mainly seen in the same phase. In heterogeneous equilibrium, implications are seen primarily on various stages. We hope this article has provided you with enough information to understand the concept of equilibrium. You can gain further knowledge and experience by experimenting practically.