Answer
$1.06\times10^{-18}$gram
Work Step by Step
Multiply mass of one oxygen molecule with 20,000. Note that $20,000 = 2\times10^{4}$ in scientific notation.
$=(5.3\times10^{-23})\times(2\times10^{4})$
$=(5.3\times2)(10^{-23}\times10^{4})$
$=10.6\times10^{-23+4}$
$=10.6\times10^{-19}$ gram
Then, write 10.6 in scientific notation.
$=1.06\times10^{1}\times10^{-19}$
$=1.06\times10^{-18}$ gram
