Question

For a given exothermic reaction, ${{K}_{p}} and {{K}^{I}}_{p}$ are the equilibrium constants at temperatures ${{T}_{1}} and \text{ }{{\text{T}}_{2}}$ respectively? Assuming that heat of reaction is constant in temperatures range between${{T}_{1}} and \text{ }{{\text{T}}_{2}}$, it is readily observation that:
(A) ${{K}_{p}}>{{K}^{I}}_{p}$
(B) ${{K}_{p}}<{{K}^{I}}_{p}$
(C) ${{K}_{p}}={{K}_{p}}$
(D) ${{K}_{p}}>\dfrac{1}{{{K}^{I}}_{p}}$

Answer 1

Exothermic reaction is a type of reaction in which heat is released. Equilibrium constant is defined as the ratio of product of concentration of product to the product of concentration of reactants each raise to the power of their respective stoichiometric coefficient.

Complete step by step solution:
Exothermic reaction can be defined as the reactions for which the overall standard enthalpy change is negative. These in general terms are known by the reactions which release heat and weak bonds are replaced by the strong bonds. Most of the experiments we do not lab involve exothermic reactions.
Given in the question:
For a given exothermic reaction ${{K}_{p}}$ is the equilibrium constant at temperature ${{T}_{1}}$
For a given exothermic reaction ${{K}^{I}}_{p}$ is the equilibrium constant at temperature ${{T}_{2}}$
To solve this problem the formulae used is:
$\log \dfrac{{{K}_{1}}}{{{K}_{2}}}=\dfrac{\Delta {{H}^{0}}}{2.303R}(\dfrac{1}{{{T}_{1}}}-\dfrac{1}{{{T}_{2}}})$
Here the temperature ${{T}_{2}}$ is greater than temperature ${{T}_{1}}$
And the ${{K}_{p}}$ is greater than ${{K}^{I}}_{p}$, then the reaction will be exothermic
Assume that temperature ${{T}_{2}}$ is greater than temperature${{T}_{1}}$, although this is not given in the question, which temperature is higher. If ${{T}_{1}}$ is greater than${{T}_{2}}$ then ${{K}^{I}}_{p}$ will be greater than${{K}_{p}}$.
Thus for an exothermic reaction when the temperature is increased the equilibrium will shift in the reverse direction and the value will decrease.

Hence the correct answer is option (A)

Note: Do not get confused between exothermic and exergonic reactions, both reactions are different, they only have similar names. Exergonic reactions are the reactions for which the overall standard Gibbs energy change will be negative. It is true that any strong exothermic reaction will be an exergonic reaction in nature.