Chemistry and Chemical Reactivity (9th Edition)

There's more mass in $3.0\times10^{23}$ molecules of adenine than in 40.0 g.
Molecular formula of adenine: $C_5N_5H_5$ Molar mass $135.13\ g/mol$ $3.0\times10^{23}\ molecule \div(6.022\times10^{23}\ molecule/mol)\times135.15\ g/mol=67\ g$