How would you determine K for the following reaction

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Discussion Overview

The discussion centers on determining the equilibrium constant (K) for the reaction between hypochlorous acid (HOCl) and cyanide (CN⁻), with participants exploring different interpretations of the reaction and the nature of the species involved. The scope includes theoretical considerations of chemical equilibrium and potential redox implications.

Discussion Character

  • Debate/contested, Conceptual clarification, Exploratory

Main Points Raised

  • One participant suggests that K refers to the equilibrium constant and proposes a formula for K_c based on concentrations of reactants and products.
  • Another participant asserts that hypochlorous acid (HOCl) is a weak acid, challenging the assumption that the reaction goes to completion.
  • A different viewpoint questions the correctness of the reaction as written, noting the absence of chlorine on the product side.
  • One participant proposes an alternative reaction product, suggesting that OCl⁻ may be more appropriate than OCN⁻.
  • Another participant introduces the possibility that the reaction could be redox-related, mentioning the existence of cyanic acid (HOCN) and questioning the half-potential for the oxidation of cyanide to cyanate.

Areas of Agreement / Disagreement

Participants express differing views on the nature of HOCl and the validity of the reaction as presented. There is no consensus on the correct interpretation of the reaction or the appropriate products, indicating ongoing disagreement.

Contextual Notes

Participants highlight uncertainties regarding the classification of HOCl, the completeness of the reaction, and the potential for redox processes, which remain unresolved.

Who May Find This Useful

Readers interested in chemical equilibrium, acid-base reactions, and redox chemistry may find the discussion relevant.

courtrigrad
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How would you determine K for the following reaction:
[tex]HOCl_{aq} + CN^{-} \rightarrow HCN_{aq} + OCN^{-}[/tex]?

You don't do [tex]\frac{1}{K_{a}}[/tex] or [tex]\frac{1}{K_{b}}[/tex]

Thanks
 
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If you mean K as in the equilibrium constant, then I think you would do the following:

[tex]K_c = \frac{[HCN][OCN^{-}]}{[HOCl][CN^{-}]}[/tex], where [] indicate the concentration in moles per liter.

If you're talking about another K, then I can't help you off the top of my head. We just started learning about equilibrium on Monday in AP Chemistry, so you may not want to trust me on this.
 
Last edited:
Perchloric acid is a strong acid, the reaction will go towards completion.
 
HOCl is not a strong perchloric acid. HOCl is a pretty weak hypochlorous acid.

There is something wrong with the reaction - where is Cl on the right side?
 
I think it should be:

[tex]HOCl_{(aq)} + CN^{-} \rightarrow HCN_{(aq)} + OCl^{-}[/tex]
 
Last edited:
That was my first idea too, but HOCN does exist (it is cyanic acid) - so perhaps the question was not acid/base related, but redox related - with cyanide being oxidized to cyanate by hypochlorous acid.

No idea what is halfpotential for cyanide/cyanate oxidation.
 

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