Answer
Please see the work below.
Work Step by Step
We know that
$PV=nRT$
This can be rearranged as:
$n=\frac{PV}{RT}$
We plug in the known values to obtain:
$n=\frac{(10^{-10})(0.001)}{(8.314)(273.15)}$
$n=4.403\times 10^{-17}moles$
Now we can find the number of molecules as
$N=nN_A$
$N=(4.403\times 10^{-17})(6.022\times 10^{23})$
$N=2.7\times 10^7 molecules$
