For ideal gases, we can say that the mole fraction,
Look up partial pressures and mole fractions if you are unsure about this. It is telling us a lot of useful information. Here's a link to the wiki:
And here is a useful example of defining ppm for gases:
So I will assume that ppm for gases means the following:
So we have 10 CO molecules for every 999,990 air molecules, or 10 moles of CO for every 999,990 moles of air.
The useful thing about ppm is that temperature and pressure don't matter (they cancel out).
See an explanation on the website below:
This means that we don't need to worry about the temperature or pressure in our calculation, we can just use the mole fraction to determine what volume the CO will take up.
So using the mole fraction law above we have:
This means that
We know that
So the volume of air will be
We can also calculate the partial pressure of the CO:
And the pressure of the air will be: