Find out the value of equilibrium constant for the following reaction at 298 K ?

To determine the equilibrium constant (K) for a given reaction at 298 K, we need to know the balanced chemical equation and the concentrations or partial pressures of the reactants and products at equilibrium. The equilibrium constant is a measure of the ratio of the concentrations of products to reactants at equilibrium, raised to the power of their respective coefficients in the balanced equation.

Understanding the Equilibrium Constant

The equilibrium constant expression for a general reaction can be represented as follows:

• For a reaction: aA + bB ⇌ cC + dD
• The equilibrium constant (K) is given by: K = [C]^c [D]^d / [A]^a [B]^b

Here, [A], [B], [C], and [D] represent the molar concentrations of the reactants and products at equilibrium, while a, b, c, and d are the coefficients from the balanced equation.

Steps to Calculate K

To find the value of K, follow these steps:

1. Write the balanced equation: Ensure that the chemical equation is balanced with respect to the number of atoms of each element on both sides.
2. Determine equilibrium concentrations: Find the concentrations of all reactants and products at equilibrium. This may involve using initial concentrations and changes that occur as the reaction proceeds.
3. Plug values into the K expression: Substitute the equilibrium concentrations into the equilibrium constant expression.
4. Calculate K: Perform the calculations to find the numerical value of K.

Example Calculation

Let’s say we have the following reaction:

2NO(g) + O2(g) ⇌ 2NO2(g)

Assume at equilibrium, the concentrations are as follows:

• [NO] = 0.1 M
• [O2] = 0.05 M
• [NO2] = 0.2 M

Now, we can write the equilibrium constant expression:

K = [NO2]^2 / ([NO]^2 [O2])

Substituting the values:

K = (0.2)^2 / ((0.1)^2 * (0.05))

K = 0.04 / (0.01 * 0.05) = 0.04 / 0.0005 = 80

Thus, the equilibrium constant K for this reaction at 298 K is 80.

Key Takeaways

Understanding how to calculate the equilibrium constant involves knowing the balanced equation and the concentrations of reactants and products at equilibrium. The value of K provides insight into the extent of the reaction; a large K indicates that products are favored, while a small K suggests that reactants are favored. Always ensure that you are using the correct units and that your reaction is balanced before performing any calculations.