[Poptimus]

Hey all,

Upon running through calculations I have hit a wall. I should be able to simply do these dilutions, but I seem to have chemists block. The question is as follows:

You will be furnished with a 10 mL mixed stock solution containing each component at 0.10 mg/mL. The components are chlorpyrifos, ethyl parathion, and malathion. The final concentration of the solution is to be 0.5 ng/μL with a final volume of 10 mL.

Just need help getting started with it. I am not sure if I should treat it as one solution or calculate the number of moles of each component.

Thanks guys.

[Hunter2]

Get equal units first. Convert mg/ml to ng/µl  What dilution factor you can see?

[Arkcon]

Just need help getting started with it. I am not sure if I should treat it as one solution or calculate the number of moles of each component.

I don't really understand what you mean by this.  Maybe you could try it both ways, and see what you get, or maybe it would be too obvious for you to continue.  If you're really stuck, try a trial run with different numbers.  For example, you have 1 M solutions of A, B, and C, you need a solution that is 0.1 M with respect to A and B and C.  What happens if you mix 3 mls of A and 3 Mls of B and 3 mls of C?  What do you get, and what more do you have to do?

[Poptimus]

I have calculated it out and the initial volume necessary would be 0.05 mL. Can anyone verify this answer?

[Hunter2]

Yes it is correct.