Question

Calculate the value of equilibrium constant for the following reaction:
$PC{l_5} \rightleftharpoons PC{l_3} + C{l_2}$

Answer 1

In a chemical reaction, chemical equilibrium is the state in which both reactants and products are present in concentrations which have no further tendency to change with time, so that there is no observable change in the properties of the system. At equilibrium, the value of the equilibrium constant is defined as the product of the concentration of the products divided by the concentration of the reactants.

Complete step by step answer:
The equilibrium state results when the forward reaction proceeds at the same rate as the reverse reaction. The reaction rates of the forward and backward reactions are generally not zero, but equal. Thus, there are no net changes in the concentrations of the reactants and products. Such a state is known as dynamic equilibrium.
The equilibrium constant of a chemical reaction is the value of its reaction quotient at chemical equilibrium, a state approached by a dynamic chemical system after sufficient time has elapsed at which its composition has no measurable tendency towards further change. For a given set of reaction conditions, the equilibrium constant is independent of the initial analytical concentrations of the reactant and product species in the mixture.
Thus, for the given chemical reaction $PC{l_5} \rightleftharpoons PC{l_3} + C{l_2}$ , the equilibrium constant at constant concentration$({K_C})$ can be written as:
${K_C} = \dfrac{{[PC{l_3}][C{l_2}]}}{{[PC{l_5}]}}$
Similarly, the equilibrium constant at constant pressure $({K_P})$ can be written as:
${K_P} = \dfrac{{{P_{C{l_3}}} \times {P_{C{l_2}}}}}{{{P_{PC{l_5}}}}}$
Where, $P =$ partial pressure of the respective gases

Note:
Thus, given the initial composition of a system, known equilibrium constant values can be used to determine the composition of the system at equilibrium. However, reaction parameters like temperature, solvent, and ionic strength may all influence the value of the equilibrium constant. A knowledge of equilibrium constants is essential for the understanding of many chemical systems, as well as biochemical processes such as oxygen transport by hemoglobin in blood and acid-base homeostasis in the human body.