Preparing a Solution using ppm and ppb -

  • #1
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I would like to prepare 50.0 g of 50 ppb Pb standard solution in 1% HNO3 gravimetrically, in a 50.0mL plastic tube from a stock solution of 50 ppm Pb.

From what I understand, this is a dilution...so C1V1 = C2V2

I like working in mg/L more than ppb and ppm so I converted

50 ppb = 0.05 mg/L
50 ppm = 50 mg/L

C1V1 = C2V2
50 mg/L V1 = (0.05 mg/L)(0.05L)
V1 = 0.00005L or 0.05 mL

so then 0.05 mL of 50 ppm Pb and 49.95 mL of HNO3.
Would this be the proper way to prepare this solution?
 

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  • #2
Bystander
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gravimetrically

0.05 mL of 50 ppm Pb and 49.95 mL of HNO3
"Gravimetrically?" Or, by volume? At this concentration, a significant fraction of solute is going to be adsorbed on the surfaces of vessels/flasks/containers; are you concerned, or have you made allowances for such an effect?
 
  • #3
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"Gravimetrically?" Or, by volume? At this concentration, a significant fraction of solute is going to be adsorbed on the surfaces of vessels/flasks/containers; are you concerned, or have you made allowances for such an effect?

This is my first time preparing a solution given the above directions. My instructions stated to prepare the solution gravimetrically. However, I could only figure out how to prepare the solution by volume, ie: 0.05 mL of 50 ppm Pb and 49.95 mL of HNO3. Would you suggest there is a more effective way to make the solution?
 
  • #4
epenguin
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I would like to prepare 50.0 g of 50 ppb Pb standard solution in 1% HNO3 gravimetrically, in a 50.0mL plastic tube from a stock solution of 50 ppm Pb.

From what I understand, this is a dilution...so C1V1 = C2V2

I like working in mg/L more than ppb and ppm so I converted

50 ppb = 0.05 mg/L
50 ppm = 50 mg/L

C1V1 = C2V2
50 mg/L V1 = (0.05 mg/L)(0.05L)
V1 = 0.00005L or 0.05 mL

so then 0.05 mL of 50 ppm Pb and 49.95 mL of HNO3.
Would this be the proper way to prepare this solution?

I doubt you do want to prepare 50 g at 50 ppb - that would be a billion liters wouldn't it?

You had better state or find out what you mean by a billion as there are two different meanings round.

If it is thousand million then you have tondilut your 50 ppm a thousand times. Burt I'm not sure you knows what this means.
 
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  • #5
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I doubt you do want to prepare 50 g at 50 ppb - that would be a billion liters wouldn't it?

I suppose 50 g refers to the mass of the solution, not of the solute.
 
  • #6
epenguin
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I misread and thought it was saying 50g of Pb! He also says 50 ml. For his practical purposes I guess it is good enough to. Insider these two the same thing.
 
  • #7
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I misread and thought it was saying 50g of Pb! He also says 50 ml. For his practical purposes I guess it is good enough to. Insider these two the same thing.

Okay, does this mean the original calculations I posted (see first post) would be correct to prepare the solution then? I can clarify with the person who wrote the directions by what the 50g refers too (either solute or solution)
 

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