19.2 Applications of Equilibrium Constants
19.2 Applications of Equilibrium Constants
Lesson Objectives
- Use experimental data to determine an equilibrium constant.
- Be able to interpret the value of an equilibrium constant to say whether the equilibrium for a particular reaction
is product-favored or reactant-favored.
Lesson Vocabulary
- ICE table: A mathematical method that can be used to determine equilibrium constants for chemical reactions
based on the Initial, Change in, and Equilibrium amounts of reactants and products.
Check Your Understanding
- Write the equilibrium constant expression for the reaction in which carbon monoxide gas decomposes into
solid carbon and oxygen gas. Write the expressions for both Kcand Kp.
Introduction
Figure19.4 shows a brown cloud over a major U.S. city. The brown color comes from nitrogen dioxide, a highly
toxic gas that exists in equilibrium with other atmospheric gases. These materials are harmful to health and contribute
to other detrimental processes, such as the formation of acid rain. The phenomenon is observed primarily in large
urban areas where there is a large amount of automobile traffic in a concentrated area. Urban locations where air
circulation is poor, such as valleys, may see an especially high amount of these gases.
Under normal conditions, NO 2 is in equilibrium with its dimeric form, N 2 O 4. N 2 O 4 is also quite toxic, but it is
colorless. This equilibrium can be written as the following chemical equation:
2NO 2 (g) N 2 O 4 (g)
Once this reaction reaches equilibrium, will the material exist mostly as NO 2 , mostly as N 2 O 4 , or as an approximately
even mixture? To answer this question, we would need to determine the equilibrium constant for this reaction at the
temperature of interest.