Can dynamic equilibrium be disrupted?

1 Answer
Jun 19, 2014

Yes, anything that changes the thermodynamic state of the system will disrupt a system previously at equilibrium.

For example, if we raise the temperature of a system containing an exothermic reaction, then the equilibrium will shift in a backward direction, generating more reactants and less products in the new equilibrium state. An endothermic reaction will shift in the opposite direction, toward products.

If a reaction produces more gaseous products than reactants (e.g., if the products have 3 moles of gas compared with only 2 for the reactants), like
#2 NO_2(g) harr 2 NO(g) + O_2(g)#
then reducing the volume of the system by compressing it will shift the equilibrium backward toward reactants. A gas-consuming reaction will shift in the opposite direction.

In general. Le Chatelier's Principle tells us that when a system initially at equilibrium is subjected to a disturbance (change of temperature, pressure, volume, density, etc.) then the system will respond in a way that tends to minimize the effect of the disturbance. So if the temperature is raised, the reaction will shift in a way that absorbs heat, or if the volume is decreased the reaction will shift in a way that reduces pressure.

Some things, however, won't affect an equilibrium. These include adding a catalyst, adding any unreactive species, or changing the pressure of a vessel containing no gaseous compounds.