How would you determine K for the following reaction

[courtrigrad]

How would you determine K for the following reaction:
$$HOCl_{aq} + CN^{-} \rightarrow HCN_{aq} + OCN^{-}$$?

You don't do $$\frac{1}{K_{a}}$$ or $$\frac{1}{K_{b}}$$

Thanks

 

[ksinclair13]

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

$$K_c = \frac{[HCN][OCN^{-}]}{[HOCl][CN^{-}]}$$, 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.

 

[GCT]

Perchloric acid is a strong acid, the reaction will go towards completion.

 

[Borek]

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?

 

[ksinclair13]

I think it should be:

$$HOCl_{(aq)} + CN^{-} \rightarrow HCN_{(aq)} + OCl^{-}$$

 

[Borek]

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.