Questions and answers on how to convert things from one unit or system to another



Postby NOR » Thu Jul 27, 2006 7:28 am

I need to make a solution that contains PAH (paraaminohippuric acid) at 25mmol/liter.
So as suggested I did like this
1. 25mmol/l divide by 1000=0.025mol/l
2. 0.025 mol/l x the MW of PAH which is 194.19g/mol =4.85475
does this mean i need to dissolve 4.85475 g of PAH in one liter to get the 25mmol/liter
However i have found out that i have little amounts of PAH
so I want to make just 100ml with a concentration of 25mmol/liter
So do i just do some ratio and proportion like:

4.85475 g PAH/1000ml =X g PAH/100ml =0.485475 g of PAH
Thus i just need to mix 0.485475 g of PAH then fill up to 100 ml
Is the concentration still 25mmol/ liter?
Posts: 18
Joined: Mon Jul 17, 2006 9:49 pm

Postby Guest » Thu Jul 27, 2006 6:42 pm

Yes, your ratio method is exactly right. You can use this method to make any amount, the substance and solvent just need to be in the right ratio.

additional question

Postby NOR » Thu Jul 27, 2006 6:49 pm

thank you so much
I have another if i were to make a a 1 liter solution (0.9% saline, already made) containing 1% PAH
is that just like getting 10 g of PAH and adding to 1000 ml of saline?thanks again in advance
Posts: 18
Joined: Mon Jul 17, 2006 9:49 pm

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