Respuesta :

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

Answer: 0.23 grams

Explanation:

According to avogadro's law, 1 mole of every substance weighs equal to its molecular mass and contains avogadro's number [tex]6.023\times 10^{23}[/tex] of particles.

To calculate the number of moles, we use the equation:

[tex]\text{Number of moles}=\frac{\text{Given molecules}}{\text{Avogadro's number}}=\frac{7.20\times 10^{20}}{6.023\times 10^{23}}=1.2\times 10^{-3}moles[/tex]

1 mole of caffeine [tex](C_8H_{10}N_4O_2)[/tex] weighs = 194 g

[tex]1.2\times 10^{-3}[/tex]  moles of  [tex](C_8H_{10}N_4O_2)[/tex] weigh = [tex]\frac{194}{1}\times 1.2\times 10^{-3}=0.23g[/tex]

Thus mass of caffeine [tex](C_8H_{10}N_4O_2)[/tex] is 0.23 grams.