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Topic: How to neutralize a HCl solution?  (Read 5899 times)

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Offline Bro-Mide

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How to neutralize a HCl solution?
« on: December 04, 2011, 06:05:09 PM »
If I have a 20% HCl in water solution.
-What is the process to neutralize it? (What chemical? is there a way to calculate how much I will need to add?
What is the salt that is produced by the reaction?

Offline Bro-Mide

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Re: How to neutralize a HCl solution?
« Reply #1 on: December 04, 2011, 06:45:28 PM »
Alright, I tried to do it with NaOH (solid crystals and 50% solution with water) I either had it pH=0 or 13. I couldnt seem to get it balanced. Im wondering if maybe i'm supposed to use a weak base so it changes slower. I also assumed the salt was HCl + NaOH = H2O + NaCl so table salt.

Would you usualy use weak base to change the pH? What base would work best?

Offline Arkcon

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Re: How to neutralize a HCl solution?
« Reply #2 on: December 04, 2011, 07:37:20 PM »
Briefly, if I wanted to neutralize a solution of strong acid, I would use the appropriate amount of strong base.  A weak base would incompletely neutralize the acid, not work slower or gentler.  The problem with your current question is you have solutions expressed as %, and you need, according to the balanced equation you have, equal molar amounts.  You have to convert your units to determine the right amounts to mix.  Have you done this sort of conversion before?  Its a pretty basic, early chemistry, sort of problem.  But the time you've mastered it in class, usually you've mastered some basic laboratory safety procedures as well, so we can be sure you should be performing this sort of thing.  So it works out well for us, liability-wise, as well.
Hey, I'm not judging.  I just like to shoot straight.  I'm a man of science.

Offline Bro-Mide

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Re: How to neutralize a HCl solution?
« Reply #3 on: December 04, 2011, 10:27:12 PM »
I know how to calculate the molar amounts.

Will it be a 1:1 molar ratio between a strong acid and strong base? When i'm really close to neutralizing the solution do you just add the base one drop at a time, like a titration?

I've been using pH strips to test. Is there a color indicator that I can use that I can easily remove without removing my dissolved product?

What are my best options for base to use? Is Sodium hydroxide the standard strong base as its makes sodium chloride as a by product?

Offline Arkcon

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Re: How to neutralize a HCl solution?
« Reply #4 on: December 05, 2011, 08:43:19 AM »
I know how to calculate the molar amounts.

Will it be a 1:1 molar ratio between a strong acid and strong base? When i'm really close to neutralizing the solution do you just add the base one drop at a time, like a titration?

Yes.  That's what the balanced equation tells you.  The (understood) 1 before the NaOH and HCl lets you know that.  You would use a different ratio in case of, for example Ca(OH)2 or H3PO4.  Its definitely worthwhile to slow down, and go dropwise, in case of some error in your measurements.

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I've been using pH strips to test. Is there a color indicator that I can use that I can easily remove without removing my dissolved product?

I haven't seen pH test strips leach large amounts of their indicator into a solution, but if absolutely no contamination is desired, then you should extract a drop, test it, and discard.  Or use a pH meter.  But fastidious people would say that you should do the same with a pH meter, to avoid contaminating product with traces of electrolyte.  Generally, for later workup, we only try to remove most of the acid, unless it interferes with later steps.

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What are my best options for base to use? Is Sodium hydroxide the standard strong base as its makes sodium chloride as a by product?

Its also cheap, so often found in the lab.  Depends on if the NaCl would interfere with your product.
Hey, I'm not judging.  I just like to shoot straight.  I'm a man of science.

Offline fledarmus

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Re: How to neutralize a HCl solution?
« Reply #5 on: December 05, 2011, 12:17:57 PM »
I've been using pH strips to test. Is there a color indicator that I can use that I can easily remove without removing my dissolved product?

I haven't seen pH test strips leach large amounts of their indicator into a solution, but if absolutely no contamination is desired, then you should extract a drop, test it, and discard.  Or use a pH meter.  But fastidious people would say that you should do the same with a pH meter, to avoid contaminating product with traces of electrolyte.  Generally, for later workup, we only try to remove most of the acid, unless it interferes with later steps.


I think the question was intended to be "As an alternative to pH strips, is there a color indicator (similar to phenolphthalein) that could be added to the solution during the titration, but that can be easily removed without removing the dissolved product after the titration is finished."

Offline Bro-Mide

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Re: How to neutralize a HCl solution?
« Reply #6 on: December 05, 2011, 07:02:29 PM »
Yes Fledarmus, that is exactly what I was asking.

Offline Arkcon

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Re: How to neutralize a HCl solution?
« Reply #7 on: December 05, 2011, 07:17:23 PM »
Hmm ... tricky.  Well, if I was trying to isolate an inorganic compound, I might use something like phenolpthalein, and then , I dunno, maybe roast it to destroy the orgainic molecule.  But that's kinda weird application.
Hey, I'm not judging.  I just like to shoot straight.  I'm a man of science.

Offline fledarmus

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Re: How to neutralize a HCl solution?
« Reply #8 on: December 06, 2011, 08:01:24 AM »
I can't think of anything either. If this is a process you will be doing a lot, it would probably be worth investing in an electronic pH meter. That will give you the instantaneous readout you are looking for in an internal color change indicator, without the contamination of your sample.

If this is a quality control process, it might even be worth investing in an auto-titrator.

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