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Topic: A problem with pH  (Read 4430 times)

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Offline Damiano0707

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Re: A problem with pH
« Reply #15 on: March 17, 2018, 06:47:54 PM »
Actually no. Could you explain me?

Offline Borek

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Re: A problem with pH
« Reply #16 on: March 18, 2018, 04:40:03 AM »
http://www.chembuddy.com/?left=pH-calculation&right=pH-amphiprotic-salt

Don't worry about the derivation, check out just the final formula - can you apply it here?
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Offline Damiano0707

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Re: A problem with pH
« Reply #17 on: March 18, 2018, 12:16:11 PM »
Sorry but I don't think I can use it.

Offline Borek

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Re: A problem with pH
« Reply #18 on: March 18, 2018, 12:49:24 PM »
You have listed both pKa values, why can't you use them?

(just in case: final formula is not the one listed on the page as the last)
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Offline Damiano0707

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Re: A problem with pH
« Reply #19 on: March 18, 2018, 03:14:45 PM »
I understood the formula is

[H+]=√(ka1*ka2)

But the problem doesn't ask the final pH but the moles of SO32-.

Offline Borek

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Re: A problem with pH
« Reply #20 on: March 18, 2018, 03:53:33 PM »
OK, try to apply it even if it doesn't do exactly what you need.
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Offline Damiano0707

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Re: A problem with pH
« Reply #21 on: March 18, 2018, 06:56:05 PM »
ph=(pKa1+pKa2)/2= 4.565

It'similar to pH given

Offline Damiano0707

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Re: A problem with pH
« Reply #22 on: March 18, 2018, 06:56:49 PM »
And now?

Offline Borek

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Re: A problem with pH
« Reply #23 on: March 18, 2018, 07:07:51 PM »
It'similar to pH given

Yes, that's exactly what I wanted you to spot!

Depending on the source of pKa values you will find that the pH given is either very close or just identical to the pH of the solution in question. Assuming the latter - what does it tell you about the composition of the solution?
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Offline Damiano0707

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Re: A problem with pH
« Reply #24 on: March 18, 2018, 07:43:57 PM »
Thanks
I understood how to continue
« Last Edit: March 18, 2018, 11:11:39 PM by Damiano0707 »

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