The chemical reaction would be written as:
CO + 2H2 = CH3OH
We need to determine first the limiting reactant from the given amounts of the reactants. Then, use this amount to relate the substances from the reaction. We calculate as follows:
1.50x10^-6 g CO ( 1 mol / 28.01 ) = 5.36x10^-8 mol CO
6.80x10^-6 g H2 ( 1 mol / 2.02 ) = 3.37x10^-6 mol H2
Therefore, the limiting reactant would be CO.
H2 left = 3.37x10^-6 mol H2 - (5.36x10^-8)(2) = 3.2628x10^-6 H2 left