Given that the 2008 concentration of CH4 in the atmosphere was 1.88 ppm, calculate the total mass of CH4 in the atmosphere in 2008. The total mass of the atmosphere was 5.1x10^18 kg and the average molar mass of the atmosphere is 29.0 g/mole
It's unclear how you are measuring this but I assume 1.88 ppm means 1.88 grams/10^6 grams air.
So 1.88 x (5.1E21g/10^6 g) = ??