LeChatelier's Principle
External Influences on the Amounts of Compounds
in a System at Chemical Equilibrium
Gary L. Bertrand            gbert@mst.edu
Missouri University of Science & Technology
discussion      the system

The System

A 10-liter expandable container is half-filled with water.  The space above the water is filled with water vapor and any gaseous compounds.  If any gaseous compounds are present, they are assumed to be ideal gases and the total pressure is 1 atm.  The compounds are assumed to exist in only one phase:  solids and gases are not soluble in either mercury or water, and aqueous compounds are neither volatile nor soluble in mercury.  The system is at equilibrium with all components of the reaction present in the designated phase.

The container may be expanded or compressed so that changes may take place at either constant volume or constant pressure.  Unless otherwise specified, all changes take place at constant temperature.  If a component is added to the system, the question refers to changes that occur after the compound has been added.