The number of grams that are in 7.62 x10^17 molecules of oxygen is 4.064 x10^-5 grams
calculation
by use of Avogadro constant find number of moles in 7.62 x10^-17
that is 1 mole = 6.02 x10^23 molecules
? = 7.62 x10 ^17 molecules
cross multiply
(1mole x 7.62 x10^17)/6.02 x10^ 23 = 1.27 x10^-6 moles
mass = mole x molar mass
molar mass of oxygen molecule = 16 x2=32g/mol
mass = 11.27 x10^-6 moles x 32 g/mol = 4.064 x10^-5 grams