Factors Affecting Equilibrium Constant

Equilibrium is attained when there is no change in the amounts of reactants and products. Chemical equilibrium is a complex process. In this, the rate of the forward reaction is equal to the rate of the backward reaction. And the relationship between the products and reactants in equilibrium is expressed by the equilibrium constant. In this article, we will learn about factors affecting equilibrium constant and how to use the equilibrium constant for predicting the direction of a reaction. 

Calculating equilibrium constant for predicting the direction of a reaction

It is important to know the direction when we deal with reversible reactions. For example, in the production of ammonia from nitrogen and hydrogen, we need to optimise the process for accuracy of formation. You can calculate the direction of a reaction by calculating its reaction quotient and equilibrium constant.

Calculating equilibrium constant

The relationship between the product and reactant in equilibrium is termed as equilibrium constant. The equilibrium constant in terms of the molar concentration of products and reactants is given as

Kc= [C]c [D]d/[A]a [B]b

Calculating reaction quotient

The reaction quotient is known by Q, and it measures the number of reactants and products in a chemical equation. The reaction quotient in terms of their molar concentration can be given as 

Qc = [C]c [D]d/ [A]a [B]b

Now, the calculation for the equilibrium constant for predicting the direction of a reaction is shown below:

• If Q = Kc, then the reaction is in equilibrium. The actual concentration equals the concentration of products and reactants at equilibrium.

• If Q < Kc, then the reaction is said to be moving forward. The initial concentration is less than the equilibrium concentrations. In this situation, more products are formed.

• If Q > Kc, then the reaction moves in the reverse direction. The initial concentrations are greater than the equilibrium concentrations. In this situation, more reactants are formed.

Factors affecting equilibrium constant meaning

What are factors affecting equilibrium constant meaning? Factors affecting equilibrium constant are those things that bring about a change in the equilibrium constant. 

Effect of change in concentration on the equilibrium constant

Equilibrium constants are not changed if you change the concentration of reactants and products present in the chemical equilibrium.

According to Le Chatelier’s Principle, if you bring about a change in concentration of products and reactants, the position of equilibrium moves so that it reverses the change you have made.

Factors affecting equilibrium constant examples

Factors affecting the equilibrium constant can be explained using this equation:

A + 3B= C + D

If you increase the concentration of C, the equilibrium moves in the reverse direction to decrease the concentration of C. If you increase the concentration of C, then the Kc constant becomes bigger, which would change the value of Kc. To stop a change in the concentration of Kc, the concentration of C would have to decrease and come to its original value. This reverses the direction of the equilibrium.

Effect of change in pressure on the equilibrium constant

This applies to a system containing only one gas. There is no change in the equilibrium constant if there is a change in the pressure of the system. According to Le Chatelier’s Principle, if you change the pressure, the equilibrium will move so that it reverses the change. 

For example, consider a chemical reaction that contains all gases. The change in partial pressure of one gas will directly or indirectly affect the Kp. And since the values of Kp can’t change unless there is a change in temperature, the equilibrium shifts in the direction of change to reverse the direction.

Effect of change of temperature on the equilibrium constant

Equilibrium constant changes if you bring about a change in the temperature of the overall reaction. For example, consider the factors affecting the equilibrium constant for a reaction, such as one involving hydrogen and iodine.

H2+ I2 = 2HI

With ΔH = -10.4 KJ / mol

The KP is PP = P2 HI/ PH2 P I2

As you can see, the value of Kp decreases as the temperature rises. It is the result of all forward reactions concerning equilibrium that are exothermic. The value of the equilibrium constant decreases as the temperature rises. The opposite happens in the case of an endothermic reaction, i.e., increasing the temperature increases the value of the equilibrium constant.

When the temperature changes, so does the position of equilibrium. The reaction moves in such a way that reverses the changes. As per Le Chatelier’s Principle, if you increase the temperature, there is a shift in equilibrium so that the temperature will be reduced again. It will accomplish this by favouring the reaction that absorbs heat.

Conclusion 

Calculating the equilibrium constant for predicting the direction of a reaction is necessary to determine the yield of the reaction. And when we calculate the direction, we get to know certain factors that affect the equilibrium constant. The factors affecting equilibrium constant are temperature, pressure, and concentration. While there is no change in equilibrium constant on change of pressure and concentration, an increase in temperature leads to a decrease in concentration and vice versa.