Mass of molecules : What is the mass (in grams of 10.0 billion sulphur dioxide `(SO_(2))` molecules?
Strategy : The molecular mass of `SO_(2)` is 64.1 u. Thus, its mole and then find the mass using Eqs(1.7).

Explanation

step 1: Accroding to Eq.(1.7)we have
Moles of `SO_(2) = ("Number of" SO_(2) "molecules")/("Avogadro's constant")`
`= (10.0xx10^(9) SO_(2) "molecules")/(6.022xx10^(23) SO_(2) "molecules mol"^(-1))`
`= 1.66xx10^(-14) mol SO_(2)`
step2 : Accroding to Eq (1.7) we have
Mass of `SO_(2) = ("moles of" SO_(2)) xx ("molar mass of" SO_(2))`
`= (1.66xx10^(-14) mol)(64.1g mol^(-1))`
`= 1.06xx10^(-12) g`
One-step calculation using conversion factors :
`? g SO_(2) = 10.0xx10^(9) SO_(2)` molecules
`xx (64.1g SO_(2))/(6.022xx10^(23) SO_(2) "molecules")`
`= 1.06xx10^(-12) g`