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Topic: Relating equilibrium constant to Ka and Kb  (Read 18107 times)

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Offline Kalibasa

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Relating equilibrium constant to Ka and Kb
« on: August 23, 2009, 03:54:45 PM »
Hi! I really don't know how to do this problem:

Calculate the value of K at 298 K for this reaction

HNO2 + NH3  ::equil:: NH4+ + NO2-

where I have tables of the Ka and Kb values

How can I find an equilibrium constant using just acid and base information?

Thanks!
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Offline MrTeo

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Re: Relating equilibrium constant to Ka and Kb
« Reply #1 on: August 23, 2009, 04:27:18 PM »
Try to split the equation in two different ones: the first expressing the dissociation of HNO2 and the second the protonation of NH3 and write their equilibrium constants.
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Offline Loyal

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Re: Relating equilibrium constant to Ka and Kb
« Reply #2 on: August 24, 2009, 03:31:16 AM »
I believe the equation to calculate the constant between a weak acid and a weak base was Ka*Kb/ Kw
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Offline MrTeo

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Re: Relating equilibrium constant to Ka and Kb
« Reply #3 on: August 24, 2009, 04:05:49 AM »
That's just what you get splitting the equation  ;)





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The way of the superior man may be compared to what takes place in traveling, when to go to a distance we must first traverse the space that is near, and in ascending a height, when we must begin from the lower ground. (Confucius)

Offline Loyal

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Re: Relating equilibrium constant to Ka and Kb
« Reply #4 on: August 24, 2009, 07:18:09 PM »
Yes.  I see some books never bother to show you how it is derived although it is a rather simple exercise in manipulating equilibrium equations.
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Offline Kalibasa

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Re: Relating equilibrium constant to Ka and Kb
« Reply #5 on: August 24, 2009, 08:37:25 PM »
Thank you!
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