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Topic: Calculate the equilibrium constant for the reaction  (Read 1922 times)

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Offline Tunechi

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Calculate the equilibrium constant for the reaction
« on: February 22, 2013, 07:14:16 PM »
Calculate the equilibrium constant for the reaction
HS(aq) + H2O(L) ------> H2S(aq) + Oh-(aq)
given that ka1 = 1.3 x 10^-7 and ka2 = 7.1 x 10^-15

Basically i looked at all the equation and concepts that i know and i don't know what approach to use on this question, its given me ka1 and ka2 which are equilibrium constants? How do i find k

k = [H2s][Oh]/[HS]

no concentrations, nothing? I tried finding the pka but idk what to do with the pkas??

Any help would be appreciated

The right answer is 7.7 x 10^-8 but i have no clue how to get it

Offline ramboacid

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Re: Calculate the equilibrium constant for the reaction
« Reply #1 on: February 22, 2013, 08:40:33 PM »
In your equation, HS- is acting as a base when it converts into H2S, so you can't go about this using purely Ka values because Ka values describe acid dissociation reactions.

What is the relationship between the equilibrium constants for the reactions
HA ::equil:: H+ + A- and H+ + A-  ::equil:: HA
where HA is a generic acid, and A- is the conjugate base?
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