# Preparing a Solution using ppm and ppb -

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1. Sep 12, 2015

### Zghakt

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?

2. Sep 12, 2015

### Bystander

"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. Sep 12, 2015

### Zghakt

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. Sep 13, 2015

### epenguin

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.

Last edited by a moderator: Sep 13, 2015
5. Sep 13, 2015

### Staff: Mentor

I suppose 50 g refers to the mass of the solution, not of the solute.

6. Sep 13, 2015

### epenguin

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. Sep 14, 2015

### Zghakt

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)