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How do I express this concentration in parts per million?



So basically what I did was, I divided 200 by 1000 then multiplied it by 100.
I got 20%, and I then multiplied it by 10,000 and got 200000 ppm.
I checked the mark scheme and it says that it's 200 ppm or 2 x 10^2. Why's that?
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Original post by FluffyCherry


So basically what I did was, I divided 200 by 1000 then multiplied it by 100.
I got 20%, and I then multiplied it by 10,000 and got 200000 ppm.
I checked the mark scheme and it says that it's 200 ppm or 2 x 10^2. Why's that?


ppm means grams per million grams

if you have 1000g you must multiply this by 1000 to get 1000,000 grams

You do the same to the 200mg

200 mg x 1000 = 200g

hence you have 200g per 1000000g = 200 ppm
Original post by charco
ppm means grams per million grams

if you have 1000g you must multiply this by 1000 to get 1000,000 grams

You do the same to the 200mg

200 mg x 1000 = 200g

hence you have 200g per 1000000g = 200 ppm


I still don't get it?!
Why would I have to convert 1000g if it's already in grams?
And, why don't I divide the 200 by 1000, they're both masses and if I divided them I'd get a concentration. Isn't mg/g equal to a concentration?
Original post by FluffyCherry
I still don't get it?!
Why would I have to convert 1000g if it's already in grams?
And, why don't I divide the 200 by 1000, they're both masses and if I divided them I'd get a concentration. Isn't mg/g equal to a concentration?


Read the first sentence of my last post ...
Original post by charco
Read the first sentence of my last post ...


I see, but isn't 200mg equal to 0.2g not 200g?
Original post by FluffyCherry
I see, but isn't 200mg equal to 0.2g not 200g?


Yes, but you are told the value in mg per 1000g

You want to know the value per 1000 x 1000 g

So logically it is 1000 x bigger than 200mg = 200g
Original post by charco
Yes, but you are told the value in mg per 1000g

You want to know the value per 1000 x 1000 g

So logically it is 1000 x bigger than 200mg = 200g


I honestly didn't understand.:unsure:
Could you please explain it again, but a bit simpler?!
(edited 8 years ago)
Original post by FluffyCherry
I honestly didn't understand.:unsure:
Could you please explain it again, but a bit simpler?!


you trollin?
Reply 8
Avatar for Alexion
Alexion
17
Original post by FluffyCherry
I honestly didn't understand.:unsure:
Could you please explain it again, but a bit simpler?!


Seems this got a bit muddled.
You've got 0.2g of Methanol in 1000g of blood.
So that's 0.2 ppt, and in order to get it in ppm, just multiply by 1000, so 0.2*1000 = 200 ppm.

Seems what you did the first time was forget to convert the mg into g, hence the factor of 103 out.
Original post by charco
you trollin?


What the hell man, why the hell would I be trolling!:lolwut:
I honestly didn't expect that sort of response from you?! :hmmm:
Original post by Alexion
Seems this got a bit muddled.
You've got 0.2g of Methanol in 1000g of blood.
So that's 0.2 ppt, and in order to get it in ppm, just multiply by 1000, so 0.2*1000 = 200 ppm.

Seems what you did the first time was forget to convert the mg into g, hence the factor of 103 out.


Ooh, I see!! Thanks a lot!:h:

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