Answer
$4.16\times10^{23}\ molecules$
Work Step by Step
Convert grams into moles using the molar mass then multiply by avagadro's number to get the number of molecules.
$22.1g\ O_{2}\times\frac{1mol\ O_{2}}{32.00g\ O_{2}}\times\frac{6.022\times10^{23}\ molecules}{1\ mol}= 4.16\times10^{23}\ molecules$