Practical Application: Copper Complex Equilibrium
This page demonstrates the application of equilibrium principles using the reaction of [Cu(H₂O)₆]²⁺ with concentrated hydrochloric acid (HCl). This example is excellent for understanding Dynamic equilibrium a Level Chemistry and Le Chatelier's principle AQA A Level Chemistry.
The equilibrium reaction is:
[Cu(H₂O)₆]²⁺ (aq) + 4Cl⁻ (aq) ⇌ [CuCl₄]²⁻ (aq) + 6H₂O
Vocabulary: [Cu(H₂O)₆]²⁺ is a blue copper aqua complex, while [CuCl₄]²⁻ is a green-yellow copper chloride complex.
The color change in this reaction allows for visual monitoring of the equilibrium position:
- Blue solution: equilibrium lies to the left (more reactants)
- Green-yellow solution: equilibrium lies to the right (more products)
The page explains how concentration and temperature changes affect this equilibrium:
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Concentration changes:
- Adding concentrated HCl shifts the equilibrium right, turning the solution greener.
- Adding distilled water shifts the equilibrium left, turning the solution bluer.
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Temperature changes:
- Heating the mixture shifts the equilibrium right (endothermic direction), producing more green [CuCl₄]²⁻.
- Cooling the mixture shifts the equilibrium left (exothermic direction), producing more blue [Cu(H₂O)₆]²⁺.
This practical example is invaluable for understanding Kc Chemistry A Level Questions and Equilibria A Level Chemistry notes.





























