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Topic: Moles and Millimoles!!!  (Read 7881 times)

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Offline neil.smif

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Moles and Millimoles!!!
« on: May 15, 2008, 10:40:20 AM »
*delete me*!!

I need to make 500ml of 250millimoles of NaAc buffer. And pH to 5 with 1M of HCL.
(The Fw of the NaAc is 82.03g)

How do I do this? I cant change the volume, nor the molarity of HCL.

It seems like I'm adding too much HCL, which would make the buffer weak, and affect the total weight per volume

Offline JGK

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Re: Moles and Millimoles!!!
« Reply #1 on: May 15, 2008, 11:42:39 AM »
*delete me*!!

I need to make 500ml of 250millimoles of NaAc buffer. And pH to 5 with 1M of HCL.
(The Fw of the NaAc is 82.03g)

How do I do this? I cant change the volume, nor the molarity of HCL.

It seems like I'm adding too much HCL, which would make the buffer weak, and affect the total weight per volume

4.1 g Na Ac, dissolve in ~450 mL water adjust to pH 5 with the acid, make up to volume with water, job done.

One question, why pH with HCl ? HAc would have been my first choice.
Experience is something you don't get until just after you need it.

Offline neil.smif

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Re: Moles and Millimoles!!!
« Reply #2 on: May 15, 2008, 12:18:52 PM »
Thanks for that. I would of also used HAc, however the people I am doing this for prefer to use HCL for some strange reason in low molarity!

Offline Borek

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Re: Moles and Millimoles!!!
« Reply #3 on: May 15, 2008, 12:24:28 PM »
4.1 g Na Ac

No. 250 mmol, not 100 mmol. 10.25 g.

neil.smif: there are programs to calculate buffers for you. See my signature ;)
ChemBuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation, titrations.info, pH-meter.info

Offline neil.smif

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Re: Moles and Millimoles!!!
« Reply #4 on: May 16, 2008, 03:53:33 AM »
Being a biologist, I dont really get to do much chemistry, so this all all new to me. Is there a simple equation that can be used to work this out? Thanks in Adnvance.

Offline Borek

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Re: Moles and Millimoles!!!
« Reply #5 on: May 16, 2008, 06:50:40 AM »
It is called Henderson-Hasselbalch equation. But it not as straightforward as you would like it.
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Offline neil.smif

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Re: Moles and Millimoles!!!
« Reply #6 on: May 16, 2008, 10:39:56 AM »
Thanks again for all your help  ;D

Offline neil.smif

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Solutions!!!
« Reply #7 on: July 01, 2008, 07:06:12 AM »
I need to dissolve 50% Hexadeconal in a 50% Dodecane Solution, does anyone know how this is done?

Thanks in advance.

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