Understanding Ligand Strength: [Cu(H2O)6]2+ to [CuCl4]2-

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Discussion Overview

The discussion revolves around the ligand substitution reaction involving the complex ion [Cu(H2O)6]2+ and its transformation into [CuCl4]2- upon the addition of concentrated hydrochloric acid. Participants explore the concepts of ligand strength, equilibrium shifts, and the terminology used to describe ligands in coordination chemistry.

Discussion Character

  • Homework-related
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant states that [Cu(H2O)6]2+ reacts with Cl- ions to form [CuCl4]2-, questioning how this occurs given that chloro is a weaker ligand than aqua.
  • Another participant suggests that the high concentration of Cl- ions may shift the equilibrium towards the formation of [CuCl4]2-, referencing Le Chatelier's principle.
  • A different participant points out that the concentration of water is typically much higher and emphasizes the importance of considering changes in geometry in the reaction.
  • One participant seeks clarification on the appropriate terminology for referring to water as a ligand, asking whether "aqua," "aqua ligand," "water," or "water ligand" is more suitable.

Areas of Agreement / Disagreement

Participants express differing views on the factors influencing the ligand substitution reaction, particularly regarding the roles of ligand strength and concentration. The discussion remains unresolved, with no consensus on the primary driving forces behind the reaction.

Contextual Notes

Participants highlight the need to consider the geometry of the complex and the relative concentrations of the reactants, which may affect the reaction dynamics. There is also ambiguity in the terminology used to describe ligands, which could impact clarity in the discussion.

AryaUnderfoot
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Homework Statement


From what I've read, [Cu(H2O)6]2+ when reacts with concentrated hydrochloric acid, the chloro ligand will displace the aqua ligand and form [CuCl4]2-

Homework Equations


[Cu(H2O)6]2+ + 4Cl- <--> [CuCl4]2- + 6H2O
( <---> means reversible reaction, I don't know how to type it out, sorry)

The Attempt at a Solution


But chloro is a weaker ligand than aqua, how can the ligand substitution reaction happen?
 
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I suspect the high concentration of the Cl- ions is sufficient to shift the equilibrium over to the right (Le Chatelier's principle) enough to cause a majority of the complex ions to undergo the ligand substitution.
 
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Water concentration is (almost) always much higher.

It is not just about the ligands, you are ignoring change of the geometry. Not that I know it is the answer here - I just see you are not taking it into account.
 
I also like to ask, since no one comment about that, is water a ligand or aqua? I know that both refer to H2O, but if I want to mention a ligand, which one of them, aqua/aqua ligand/water/water ligand, is more appropriate?
 

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