Chemistry · Ch 8 — Physical and Chemical Equilibrium
Effect of inert gas
8.8.5
Effect of inert gas
An inert gas is one that does not react with any of the species involved in a given equilibrium. Adding such a gas to an equilibrium system held at constant volume raises the total number of moles of gas present in the container, and so raises the total pressure of the container -- but because the volume available to each of the reacting gases has not changed, each species' own partial pressure (and hence its concentration) stays exactly as it was before the inert gas was added. Consequently, at constant volume, adding an inert gas has no effect at all on the position of equilibrium. …
Table 8.3Effect of concentration, pressure, temperature, catalyst and inert gas on equilibrium
| Condition | Stress | Direction in which equilibrium shifts |
|---|---|---|
| Concentration | Addition of reactants (increase in reactant concentration); Removal of products (decrease in product concentration) | Forward reaction |
| Concentration | Addition of products (increase in product concentration); Removal of reactants (decrease in reactant concentration) | Reverse reaction |
| Pressure | Increase of pressure (decrease in volume) | Reaction that favours fewer moles of gaseous molecules |
| Pressure | Decrease of pressure (increase in volume) | Reaction that favours more moles of gaseous molecules |
| Temperature (alters equilibrium constant) | Increase (high T) | Towards endothermic reaction |
| Temperature (alters equilibrium constant) | Decrease (low T) | Towards exothermic reaction |