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Topic: analytical chemistry  (Read 16795 times)

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Offline pragathi

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analytical chemistry
« on: August 06, 2008, 07:21:36 AM »
how to prepare 2%nitric acid from 67-70%nitric acid?
How many ml we need to take from 67-70%nitric acid?

Offline enahs

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Re: analytical chemistry
« Reply #1 on: August 06, 2008, 07:29:59 PM »
68.5/2 = ?

Offline JGK

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Re: analytical chemistry
« Reply #2 on: August 07, 2008, 07:55:16 AM »
2% v/v = 2mL pure HNO3 per 100 mL water

1000 mL of 2% v/v HNO3 contains 20 mL of 100% HNO3

therefore if the HNO3 is 67% pure it will require 20/(67/100)=29.9 mL

if the HNO3 is 70% pure it will require 20/(70/100)=28.6 mL

Mean value = 29.25 mL
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Offline Borek

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Re: analytical chemistry
« Reply #3 on: August 07, 2008, 09:39:05 AM »
2% v/v

Why v/v? Question didn't ask for v/v, most likely it was about w/w. Not that it changes the result much.
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Offline JGK

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Re: analytical chemistry
« Reply #4 on: August 08, 2008, 07:48:27 AM »
2% v/v

Why v/v? Question didn't ask for v/v, most likely it was about w/w. Not that it changes the result much.

Just an assumption as the HNO3 is supplied as a solution and the % content on spec sheet from supplier is based on  liquid titration
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Offline enahs

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Re: analytical chemistry
« Reply #5 on: August 08, 2008, 08:01:12 AM »
You guys sure are making it complicated for a solution that is 67-60% pure.   ;)

The average value, 68.5/2 (you want to go from 68.5% to 2%) gives a dilution factor of 34.25.
1000mL/34.25 = 29.2 mL

Which is essentially the same answer JGK's method get when you round after the math.

Offline Borek

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Re: analytical chemistry
« Reply #6 on: August 08, 2008, 08:56:16 AM »
What if I tell you that you need 21 mL per L?

What is the density of stock nitric acid?
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Offline enahs

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Re: analytical chemistry
« Reply #7 on: August 08, 2008, 06:12:57 PM »
Yeah, but you changes to w/w. Given the vagueness of the question I went with v/v, as did JGK!

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