======Copper Chloride Equilibrium======


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**Alternative titles:** Copper(II) Complex Ion Equilibrium
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====Summary====                   
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====Procedure====  
  - Prepare a test tube half filled with 1.5 M copper(II) chloride solution.  
  - Use a dropper to divide the solution evenly into five test tubes.  
  - To Tube 2, add solid calcium chloride in small amounts, dissolving each portion until no more dissolves, and note the color change.  
  - To Tube 3, add enough ethyl alcohol to triple the solution’s volume, mix, and observe the color.  
  - Place Tube 4 in a hot-water bath, heat until warm, and observe the color change.  
  - Place Tube 5 in an ice-water bath, cool thoroughly, and observe the color change.



====Links==== 
Colorful Copper Equilibrium - Tommy Technetium: 
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Effect of Temperature on Chemical Equilibrium using Copper Complexes - Chem Ed Xchange: 
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📄 Complex Ions of Copper(II) (Cu2+) (Page 4) - Science Learning Centre: [[https://www.chemedx.org/blog/effect-temperature-chemical-equilibrium-using-copper-complexes]]\\


====Variations====
None



====Safety Precautions====
  * Wear safety goggles and lab coat.  
  * Handle copper(II) chloride with care; it is toxic and harmful if ingested.  
  * Avoid skin contact with copper solutions and calcium chloride.  
  * Ethyl alcohol is flammable; keep away from flames or sparks.  
  * Use caution with hot water baths to avoid burns.  
  * Do not pour solutions down the drain.




====Questions to Consider====
  * What are the colors of the different copper complexes? (CuCl4^2– is green, Cu(H2O)4^2+ is light blue.)  
  * How does adding chloride ions shift the equilibrium? (It favors CuCl4^2– formation, giving a green color.)  
  * Why does cooling the solution affect the position of equilibrium? (The equilibrium is temperature dependent; cooling favors one complex, heating favors the other.)  
  * How does adding ethyl alcohol affect the equilibrium? (It reduces the effective dielectric constant of the solvent, changing ion stabilization and shifting equilibrium.)