Mole conversion problems

[Hkhan]

1. Here is a mole conversion question I am having a hard time.

 

Medical experts generally believe a level of 27micrograms
Pb(lead) per deciliter of blood poses a significant health risk (1dl = .1 L)

 

Express this level in the unit mol Pb/L blood.

Express your answer using two significant figures.

and this one

2. During a severe episode of air pollution, the concentration of lead in the air was observed to be 3.01 micrograms Pb/m^3 .

How many Pb(lead) atoms would be present in a 0.500 -- L sample of this air (the approximate lung capacity of a human adult)?

These are my questions i am more looking forward to a great explanation rather than the answer(if you explain it to me without the answer that would be even better). I know how to solve mole conversions but i have no idea how to tackle these problems.

Thank you

Edited February 13, 2013 by Hkhan