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Topic: Change of pH when adding KOH/HCOOH  (Read 3107 times)

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Offline addcon

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Change of pH when adding KOH/HCOOH
« on: November 10, 2014, 05:28:22 AM »
Hello all.

Say you have 10 m3 of a 50 % potassium formate solution mixed with inhibitors.
You analyze it and get a pH = 7.5 but you need the pH to be 10.
Is it possible to calculate how much 50% KOH you need to add to get a pH = 10 ?

I am a process engineer with very little experience regarding chemistry so help would be much appreciated.

Offline billnotgatez

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Re: Change of pH when adding KOH/HCOOH
« Reply #1 on: November 10, 2014, 08:29:49 AM »
Did you mean HCOOK instead of HCOOH in your title?

Can we assume you have read the forum rules which require you show some thoughts on how to solve your question

Offline Borek

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Re: Change of pH when adding KOH/HCOOH
« Reply #2 on: November 10, 2014, 03:39:24 PM »
Is it possible - yes.

Is it easy - no. You can get a trivial answer that ignores changes of ionic strength of the solution (and pH of the solution prepared based on these results will be off by several tenths of a unit). Getting better answer requires experimental coefficients (that can be already tabulated). Best approach is to first estimate amount of the KOH required using a trivial approach, then to fine tune this answer experimentally, titrating sample of the original solution. That can be tricky, as typical glass pH electrodes don't survive for long in concentrated alkaline solutions.
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