Which of the following choices is the equilibrium constant of a reaction?
A. [tex]$K_{ eq }=[$[/tex] reactants [tex]$]+[$[/tex] products [tex]$]$[/tex]
B. [tex]$K_{\text {eq }}=$[/tex] [products][reactants]
C. [tex]$K_{\text {eq }}=\frac{\text { [reactants] }}{\text { [products] }}$[/tex]
D. [tex]$K_{\text {eq }}=\frac{\text { (products) }}{\text { [reactants] }}$[/tex]
Answer (2)
The equilibrium constant, K e q , represents the ratio of products to reactants at equilibrium.
The general formula for K e q is K e q = [Reactants] [Products] .
Option D, K eq = [reactants] (products) , matches this definition.
Therefore, the correct answer is D .
Explanation
Understanding the Problem The question asks us to identify the correct formula for the equilibrium constant ( K e q ) from the given options. The equilibrium constant relates the concentrations of reactants and products at equilibrium.
Recalling the Definition of Equilibrium Constant The equilibrium constant, K e q , is defined as the ratio of the concentrations of products to the concentrations of reactants, each raised to the power of their stoichiometric coefficients. In a simple reaction where reactants convert to products, the equilibrium constant is expressed as: K e q = [Reactants] [Products] .
Comparing Options with the Definition Now, let's compare the given options with the correct definition:
A. K e q = [ reactants ] + [ products ] - This is incorrect because it involves addition, not a ratio.
B. K eq = [products][reactants] - This is incorrect because it multiplies the concentrations instead of dividing.
C. K eq = [products] [reactants] - This is incorrect because it has the reactants in the numerator and the products in the denominator, which is the inverse of the correct definition.
D. K eq = [reactants] (products) - This is the correct formula, matching the definition of the equilibrium constant.
Conclusion Therefore, the correct answer is D.
Examples
The equilibrium constant is crucial in various real-world applications. For example, in the Haber-Bosch process, which synthesizes ammonia ( N H 3 ) from nitrogen ( N 2 ) and hydrogen ( H 2 ), the equilibrium constant helps determine the optimal conditions (temperature and pressure) to maximize ammonia production. By understanding and manipulating the equilibrium constant, chemists and engineers can optimize industrial processes, design new materials, and develop more efficient chemical reactions. It also helps predict the extent to which a reaction will proceed, which is vital in fields like environmental science for predicting pollutant levels and in biochemistry for understanding enzyme-catalyzed reactions.
The equilibrium constant, represented as K e q , describes the ratio of products to reactants at equilibrium and is expressed as K e q = [Reactants] [Products] . Among the options provided, the correct one is D , which accurately reflects this definition. Understanding this concept is essential for predicting the behavior of chemical reactions.
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