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Buffer question

Lets say we have a buffer mixture of ethanoic acid and sodium ethanoate.

I know adding another acid(ie HCl) would increase the concentration of ethanoic acid and decrease the concentration of ethanoate ions.

But what if more ethanoic acid is added to the buffer mixture? Considering the anions of this acid will also affect the equilibrium of the buffer, would the ethanoate ion concentration still decrease? I know the ethanoic acid concentration has to increase, but I'm still lost about the ethanoate ions.

I also have a second question. Can you consider 1/time(in seconds) to be the same as the rate of reaction?

Thanks in advance.
Reply 1
Avatar for Pigster
Pigster
20
Adding EtOOH would move the equilibrium to the RHS, increasing [H+] (therefore reducing the pH a bit) and also increasing [Et-] (every H+ formed must also form an Et-).

1/t = rate, only for reactions in which you have a constant change in something, e.g. a clock reaction. Better to say rate is proportional to 1/t.
(edited 9 years ago)
Original post by Trainz
Lets say we have a buffer mixture of ethanoic acid and sodium ethanoate.

I know adding another acid(ie HCl) would increase the concentration of ethanoic acid and decrease the concentration of ethanoate ions.

But what if more ethanoic acid is added to the buffer mixture? Considering the anions of this acid will also affect the equilibrium of the buffer, would the ethanoate ion concentration still decrease? I know the ethanoic acid concentration has to increase, but I'm still lost about the ethanoate ions.

I also have a second question. Can you consider 1/time(in seconds) to be the same as the rate of reaction?

Thanks in advance.


The units of rate is determined by the order of the reaction, only if it's zero order will it be 1/t

(edited 9 years ago)
Reply 3
Avatar for Pigster
Pigster
20
Original post by langlitz
The units of rate is determined by the order of the reaction, only if it's zero order will it be 1/t



First order!
Original post by Pigster
First order!

Actually, after checking my notes, we're both wrong. The units of rate are always moldm−3s−1mol dm^{-3} s^{-1} .
It's the units of the rate constant, k, which are determined by the order
Reply 5
Avatar for Pigster
Pigster
20
What are the units for rate in the disappearing clock reaction, where you don't know n?

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