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Titration of CH3COONa with HCl and pKa determination from half equivalence point
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Alan Murrie
Titration of CH3COONa with HCl and pKa determination from half equivalence point
When you titrate a base like ammonia (pKa of conjugate acid around 9.5) with hydrochloric acid, you can see that it buffers in the basic region and the equivalence point is in the acidic region:
When you try the same with acetate (pKa of conjugate acid around 4.8), if buffers in the acidic region, and the equivalence point is in the acidic region:
(Sorry, bad copy and past job. The start of the curve should be in the basic region, with an initial sharp drop to the buffer region)
Here is a better graph, courtesy of EdV:
As you will find, it is difficult to distinguish the buffering region from the region past the equivalence point. Other than that, it is possible to do this, and there is nothing wrong with that.
When you titrate a base like ammonia (pKa of conjugate acid around 9.5) with hydrochloric acid, you can see that it buffers in the basic region and the equivalence point is in the acidic region:
When you try the same with acetate (pKa of conjugate acid around 4.8), if buffers in the acidic region, and the equivalence point is in the acidic region:
(Sorry, bad copy and past job. The start of the curve should be in the basic region, with an initial sharp drop to the buffer region)
Here is a better graph, courtesy of EdV:
As you will find, it is difficult to distinguish the buffering region from the region past the equivalence point. Other than that, it is possible to do this, and there is nothing wrong with that.
Weird that the only upvote is from me. One thing I have noticed is that pH problems, including titration curves, tend not to get much love here. Oh well.More
. If you have any use for it, feel free to use it and annotate, etc., as you please. I did not bother to run the ammonia versus HCl, but it is trivial to do so. I upvoted, by the way. I will leave the figure up for a couple of days. Ignore the M-B stuff: it was for a physics SE comment.More
When you titrate a base like ammonia (pKa of conjugate acid around 9.5) with hydrochloric acid, you can see that it buffers in the basic region and the equivalence point is in the acidic region:
When you try the same with acetate (pKa of conjugate acid around 4.8), if buffers in the acidic region, and the equivalence point is in the acidic region:
Here is a better graph, courtesy of EdV:
As you will find, it is difficult to distinguish the buffering region from the region past the equivalence point. Other than that, it is possible to do this, and there is nothing wrong with that.
When you titrate a base like ammonia (pKa of conjugate acid around 9.5) with hydrochloric acid, you can see that it buffers in the basic region and the equivalence point is in the acidic region:
When you try the same with acetate (pKa of conjugate acid around 4.8), if buffers in the acidic region, and the equivalence point is in the acidic region:
Here is a better graph, courtesy of EdV:
As you will find, it is difficult to distinguish the buffering region from the region past the equivalence point. Other than that, it is possible to do this, and there is nothing wrong with that.
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