# Characterstics and Factors Influencing Equilibrium constant

Characteristics of Equilibrium Constant

1. It has a definite value for every chemical reaction at a given temperature.

2. It is independent of concentrations of the reactants and products.

3. It is not effected by the presence of catalyst.

4. It is a convenient measure of the extent to which the reaction proceeds in a particular direction at a given temperature.

Factors Influencing Equilibrium Constant

1. Stoichiometic representation of reaction: Consider the following reactions: $N_2 + O_2 \rightleftharpoons 2NO \hspace{3mm} \text{and} \hspace{3mm} \dfrac{1}{2}N_2 + \dfrac{1}{2}O_2 \leftrightharpoons NO$ $K_c = \dfrac{[NO]^2}{[N_2][O_2]} K_c = \dfrac{[NO]}{[N_2]^{1/2}[O_2]^{1/2} } \\[3mm] \therefore K_c = (K_c)^2$

2. The mode of representing the change: Consider the equilibrium mixture of $N_2, O_2 \text{and} NO$ $N_2 + O_2 \leftrightharpoons 2NO \hspace{3mm} \text{and} \hspace{3mm} 2NO \rightleftharpoons N_2 + O_2$  $\therefore K_c = 1/K_c$

3. Temperature: Equilibrium constant changes with temperature as: $\log_{10} \dfrac{K_2}{K_1} = \dfrac{\Delta H}{2.303}[\dfrac{T_2- T_1}{T_1T_2}]$

Where $\Delta H$ is change in enthalpy of the reaction, other terms are as usual.

Importance of equilibrium constant:

(i)                  To find equilibrium concentrations

(ii)                 To find the measurement of extent of reaction.

Extent of forward reaction $\propto K$

I.e. Higher value of $K_c or K_p$ means reaction is going to complete.

(iii) Stability of products $\propto K_c or K_p$ $N_2 + O_2 \leftrightharpoons 2NO_2, K_c = 8.7 \times 10^{-10}$ $N_2 + O_2 \leftrightharpoons 2NO, K_c = 6.5 \times 10^{-16}$

i. e., $NO_2$ is more stable then NO here.

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