Le Chatelier's Principle
Equilibrium System
CoCl42−(blue) + 6H2O ⇌ Co(H2O)62+(pink) + 4Cl− ΔH > 0 (endothermic)
Observations
Equilibrium Position
The Chemistry
CoCl₄2−(aq) + 6H2O(l) ⇌ Co(H2O)62+(aq) + 4Cl−(aq)
This is the cobalt chloride equilibrium system. The forward reaction is endothermic. Adjust temperature, add HCl or dilute with water to see Le Chatelier's Principle in action.
About Le Chatelier's Principle
Le Chatelier's Principle states that if a system at equilibrium is disturbed, the system will shift in the direction that partially counteracts the change and re-establishes equilibrium. This applies to changes in concentration, temperature and pressure (for gaseous systems).
In the cobalt chloride system, the blue tetrachloro complex (CoCl42−) is in equilibrium with the pink hexaaqua complex (Co(H2O)62+). Since the forward reaction is endothermic, increasing temperature shifts equilibrium to the right (more pink). Adding Cl− ions shifts it to the left (more blue). Diluting with water shifts it to the right (more pink).