A day earlier, at BASIS Phoenix, I'd sat in on a 6th - grade chemistry class that was practicing converting grams to molar mass with the question, «How many mole of Sn atoms are there in 0.0126 grams of Sn?» (educationnext.org)
As we are not told we can assume equal volume and pressure applies and hence molar mass is a necessary requirement. (principia-scientific.org)
More recent figures suggest that 44 % of this remains in the atmosphere, so using that percentage for the 19th century indicates an increase in atmospheric carbon of 33 GtC, or 15.5 ppmv based on an atmosphere mass of 5148 teratonnes and a CO2 - to - air molar mass ratio of 12/28.97. (judithcurry.com)