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Topic: Diluting 5 N sulfuric acid  (Read 3965 times)

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Offline jajabor

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Diluting 5 N sulfuric acid
« on: October 24, 2013, 10:10:31 AM »
I am trying to dilute 5N sulfuric acid ( 1 in 20). I used 100 ml of 5N sulfuric acid and 1900 ml of water to make 2000 ml of diluted sulfuric acid. However, my coworker said it was wrong. It should be 720 ml of sulfuric acid and 1280 ml of water and I have to consider that it is 5N sulfuric acid. I am confused now. Why is it 720 ml of sulfuric acid? Any help?

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Re: Diluting 5 N sulfuric acid
« Reply #1 on: October 24, 2013, 12:21:26 PM »
No idea what he means, but then description of what you are doing is rather cryptic.

If you are told "dilute 5N sulfuric acid 1:20" you are doing OK. But is it what you are told to do, or is it your interpretation of what to do?
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Offline jajabor

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Re: Diluting 5 N sulfuric acid
« Reply #2 on: October 24, 2013, 01:46:29 PM »
No idea what he means, but then description of what you are doing is rather cryptic.

If you are told "dilute 5N sulfuric acid 1:20" you are doing OK. But is it what you are told to do, or is it your interpretation of what to do?

I am performing titration to determine the percentage of glycerin present in suppositories. In USP monographs it says "Transfer an accurately weighed quantity of Suppositories, equivalent to about 250 mg of glycerin, to a 250-mL volumetric flask. Dissolve in water, dilute with water to volume, and mix. Pipet 5 mL of this solution into a 250-mL conical flask, and add 50.0 mL of a reagent prepared by mixing 40 mL of dilute sulfuric acid (1 in 20) with 60 mL of potassium periodate solution (1 in 1000) acidified with 3 to 5 drops of sulfuric acid. " I have 5N sulfuric acid in the lab and I am using it.

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Re: Diluting 5 N sulfuric acid
« Reply #3 on: October 24, 2013, 02:22:36 PM »
add 50.0 mL of a reagent prepared by mixing 40 mL of dilute sulfuric acid (1 in 20)

You are misreading the procedure. You need an acid that is equivalent to one prepared by mixing stock H2SO4 (98% w/w) with water 1:20.

<a href="http://www.youtube.com/v/tkUWxXLUmsU" target="_blank" class="new_win">http://www.youtube.com/v/tkUWxXLUmsU</a>

First step - mixing stock solution (98% w/w) with water 1 in 20 to find target concentration.

Second step - finding volumes that have to be mixed if you start with 5 N solution (2.5 M). Your coworker is right about the ballpark (even 10% error shouldn't matter in this case).
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Offline jajabor

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Re: Diluting 5 N sulfuric acid
« Reply #4 on: October 24, 2013, 02:53:33 PM »
add 50.0 mL of a reagent prepared by mixing 40 mL of dilute sulfuric acid (1 in 20)

You are misreading the procedure. You need an acid that is equivalent to one prepared by mixing stock H2SO4 (98% w/w) with water 1:20.

<a href="http://www.youtube.com/v/tkUWxXLUmsU" target="_blank" class="new_win">http://www.youtube.com/v/tkUWxXLUmsU</a>

First step - mixing stock solution (98% w/w) with water 1 in 20 to find target concentration.

Second step - finding volumes that have to be mixed if you start with 5 N solution (2.5 M). Your coworker is right about the ballpark (even 10% error shouldn't matter in this case).

Ahh..thank you for clarifying this.  :)I really appreciate it.

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