Adding salt and no shift in equilibrium?

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Davis Chong 4H
Posts: 17
Joined: Wed Sep 21, 2016 2:56 pm

Adding salt and no shift in equilibrium?

Postby Davis Chong 4H » Mon Nov 28, 2016 8:16 pm

I believe a similar question was asked in class but I still didn't understand.
Using the example in the course reader pg 170
Acidic bufer Ch3COONa
When adding the CH3COO from the salt, wouldn't the equilibrium just shift the CH3COO- in accordance with its equilibruim constant to maintain the ratio?

Akshay_Manjarekar_3C
Posts: 9
Joined: Wed Sep 21, 2016 2:58 pm

Re: Adding salt and no shift in equilibrium?

Postby Akshay_Manjarekar_3C » Mon Nov 28, 2016 8:33 pm

For the example on Pg 170, I believe the reason it does not happen that way is because the K value is so small that acetic acid wants to remain as such without dissociating. When we add the conjugate base by adding the salt, some of it WILL be affected by equilibrium with H+ but it is not enough to make any significant changes to the concentration of the added conjugate base. Hence, what we observe is buffer solution in which the weak acid is in equilibrium with its conjugate base rather than Hydronium ions. Hope that helped! :)

Jared Gao 3G
Posts: 16
Joined: Wed Sep 21, 2016 2:58 pm

Re: Adding salt and no shift in equilibrium?

Postby Jared Gao 3G » Tue Nov 29, 2016 2:39 pm

Could you clarify on how adding the salt with the conjugate base would affect the Hydronium concentration? I understand that it increases the conjugate base concentration in order to buffer the solution. Also, do we factor in the hydronium concentration when we consider the equilibrium constant of this reaction?


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