The number of molecules in a gram of a substance is given by:

Number of molecules = (Mass of substance in grams) / (Molar mass of substance in grams per mole)

The molar mass of CO2 is 44.01 g/mol, while the molar mass of H2 is 2.016 g/mol.

Therefore, the number of molecules in a gram of CO2 is:

Number of molecules in 1 gram of CO2 = (1 g) / (44.01 g/mol) = 0.0227 mol

The number of molecules in a gram of H2 is:

Number of molecules in 1 gram of H2 = (1 g) / (2.016 g/mol) = 0.496 mol

So, a gram of H2 has more molecules than a gram of CO2.