This preview shows pages 1–2. Sign up to view the full content.
This preview has intentionally blurred sections. Sign up to view the full version.View Full Document
Unformatted text preview: THE CONCEPT OF EQUILIBRIUM Most chemical reactions are to some extent reversible. At the start of a reversible process, the reaction proceeds toward the formation of products. As soon as some product molecules are formed, the reverse process the formation of reactant molecules from product molecules begins to take place. Chemical equilibrium is reached when the rates of forward and reverse reactions are equal and the concentrations of the reactants and products no longer change with time. A chemical equilibrium reaction involves different substances as reactants and products. Equilibrium between two phases of the same substance is called physical equilibrium , because the changes that occur are physical changes. (The vaporization of water in a closed container at a given temperature is an example of physical equilibrium). The Equilibrium Constant Consider the chemical reaction involving nitrogen dioxide and dinitrogen tetroxide. N 2 O 4 (g) 2NO 2 (g) Experimental data for this reaction is given as follows: The NO 2- N 2 O 4 System at 25 C Initial Concentrations (M) Equilibrium Concentrations (M) Ratio of Concentrations at Equilibrium [NO 2 ] [N 2 O 4 ] [NO 2 ] [N 2 O 4 ] [NO 2 ] [N 2 O 4 ] [NO 2 ] 2 [N 2 O 4 ] 0.000 0.670 0.0547 0.643 0.0851 0.00465 0.0500 0.446 0.0457 0.448 0.102 0.00466 0.0300 0.500 0.0475 0.491 0.0967 0.00460 0.0400 0.600 0.0523 0.594 0.0880 0.00460 0.200 0.000 0.0204 0.0898 0.227 0.00463 The gas concentrations are given in molarity (M), which can be calculated from the...
View Full Document