Expressing Equilibrium Constants for Chemical Reactions

To express an equilibrium constant for a chemical reaction, we examine the balanced chemical equation and apply the law of mass action. For example, suppose we want to express the equilibrium constant for the reaction  

The equilibrium constant is [NO2] raised to the fourth power multiplied by [O2] raised to the first power divided by [N2O5] raised to the second power  

Notice that the coefficients in the chemical equation become the exponents in the expression of the equilibrium constant. 

EXAMPLE 14.1 Expressing Equilibrium Constants for Chemical Equations 

The equilibrium constant is the equilibrium concentrations of the products raised to their stoichiometric coefficients divided by the equilibrium concentrations of the reactants raised to their stoichiometric coefficients. 

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