Skill 9.2 Solving problems involving equilibrium constants and reaction quotients

Skill 9.2 Solving problems involving equilibrium constants and reaction quotients 

Earlier, we saw how the concentrations of reactants and products at equilibrium remain constant because the forward and reverse reactions take place at the same rate. We also saw how this equilibrium responds to a perturbation in one concentration by altering every concentration in a well-defined way until equilibrium is reestablished. In the present section, we will present a mathematical expression that relates these concentrations and defines the law that governs equilibrium. 

In this equation, Keq is a constant value called the equilibrium constant. Product concentrations raised to the power of their stoichiometric coefficients are placed in the numerator and reactant concentrations raised to the power of their coefficients are placed in the denominator. 

Every reaction has a unique value of Keq that varies only with temperature. Alternate subscripts are often given to the equilibrium constant. Kc or K with no subscript is often used instead of Keq to represent the equilibrium constant. 

Other subscripts are used for specific reactions as described in the following section. 

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