1. The problem statement, all variables and given/known data If the ozone concentration in a particular sample of air were 25 dobson units, what sould this concentration be in: a)ppm b) %(v/v) 2. Relevant equations 1 dob = 2.69*10^20 ozone molecules / m^2 http://en.wikipedia.org/wiki/Ozone 3. The attempt at a solution The question is asking the concentration whereas dobsons are measured molecules per surface area. How do I go about doing this since the units don't seem to agree? Also for concentration problems, I will need to know the solution which is a mixture of air but what compositions are they? The solute is ozone.