What is the mass, in grams, of 7.20×1020 molecules of caffeine, c8h10n4o2?

To determine the mass, you need to know the molecular weight of the c8h10n4o2 . The molecular weight of c8h10n4o2 would be: 8*12 + 10*1 + 4*14 + 2*16= 194g/mol.
To convert the number of molecules into moles, you need to divide it with 6.02 * 10^23. The calculation of the mass of c8h10n4o2 would be: 
(7.20×10^20 molecules)  /(6.02 * 10^23 molecule/mol)  * 194g/mol= 232 * 10^-3 grams= 0.232 grams

Idk the answer sorry

Density and pressure