Chemical Forums
Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: Periodic Table of Noob on October 31, 2008, 06:41:43 AM
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Hi everyone!
I have a question about PPM. I have to solve the PPM of Fluoride in a standard of NaF. The amount of NaF is 1.0534g and the volume is 0.250L. I've found the molarity to be 0.1M.
So after that I did PPM = 0.1M * 41.99 (mw of NaF) * 1000 = 4213.59PPM.
This is the PPM of NaF in the solution, but how do I get the PPM of F?
Is it just the same, or do I have to substitute the mW of Fluorine into the PPM equation?
Thanks.
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Exactly in the same way - use mass of fluoride instead of NaF
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Ah awesome, thanks for the clarification :)
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Just another question!
The answer came to be 1900ppm. This is in a 250ml solution.
If I were to take 10ml of the solution and dilute it to 100ml, then find the ppm, is it as simple as dividing the ppm by 25?
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If I were to take 10ml of the solution and dilute it to 100ml, then find the ppm, is it as simple as dividing the ppm by 25?
No. You took 10/250 and diluted it 10 times - so you have to divide by 25 first, and by 10 later.
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If I were to take 10ml of the solution and dilute it to 100ml, then find the ppm, is it as simple as dividing the ppm by 25?
No. You took 10/250 and diluted it 10 times - so you have to divide by 25 first, and by 10 later.
Why do you need to divide by 25 at all?
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Because you took 1/10 out of the 250, so you have 1/25 of the PPM.
I'm not sure if I explained that quite well lol.
You take 10ml from the 250ml, so you have 10/250 PPM = 1/25 PPM.
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Hmm, can't seem to edit my post again. But then yeah so you have 10ml (1/25 PPM) and you dilute that to 100ml so then you divide it by 10 again. and so the PPM gets even smaller (since it's now in 100ml rather than 10ml).
Correct me if I'm wrong!
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You're wrong.
If you have 250ml of solution that is 100ppm and take a 10ml aliquot of that solution that 10ml aliquot is still a 100ppm solution.
If you then dilute that 10ml sample to 100ml you get a 10ppm solution.
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If I were to take 10ml of the solution and dilute it to 100ml, then find the ppm, is it as simple as dividing the ppm by 25?
No. You took 10/250 and diluted it 10 times - so you have to divide by 25 first, and by 10 later.
Why do you need to divide by 25 at all?
I can't believe I wrote it >:(
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I can't believe I wrote it >:(
You do, actually, hate ppm as a unit of measure, don't you? ;D
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I can't believe I wrote it >:(
You do, actually, hate ppm as a unit of measure, don't you? ;D
I don't like its ambiguity, but as long as it is used in a well defined way, I have nothing against :)
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Hmm I see. I better fix up my calculations then!