If you had 500 mL of a 20 ppm solution, how would you make 500mL of a 500 ppb solution?

Question

What equation is needed?

Answer 1

The equation for dilution is

C1*V1=C2*V2 as long as you express concentration s in the same units and volumes in the same units you don't care exactly what units they are.

In your case we keep mL as unit for volume.
1 ppm =1000 ppb so 20 ppm =20000 ppb

In order to make 500 mL of 500 ppb you need
V1= (C2/C1)*V2 =(500/20000)*500 = 12.5 mL

So you take 12.5 mL of the 20 ppm solution, put it in a 500 mL volumetric cylinder, add solvent to reach 500 mL, mix and you're done.

Answer 2

Do you mean ppm or ppb?

If its 500ppm, add 12L of water - you want to make it 25 times weaker, which means adding 25 times more water, as you can't remove 24/25th of the soluble substance! Thus 500mL x 25 = 12.5L, minus the 500mL you began with.

If its 500ppb, it depends on whether you are using UK or US billions. If its UK billions (a thousand million) you need to add 12,499.5L, and if its US billions (a million million) you need to add12,499,999.5mL.

So make sure you've got a big bucket. :)

Of course, you could do it the way given in the next answer, which requires a smaller bucket!!! pmsl

Answer 3

no

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no