Where $N_A="Avogadro's number"$ $=$ $6.022xx10^23*mol^-1$
$"Number of moles"$ $=$ $"Mass"/"Molar mass"$
$=$ $(27*g)/(54.00*g*mol^-1)=0.500*mol$
And thus $"Number of molecules"$ $=$ $6.022xx10^23*mol^-1$
$=$ $3.011xx10^23$ $OF_2$ molecules..........
What is the oxdation number of oxygen in this molecule?