Total number of atoms present in 64 gm of ${\mathrm{SO}}_2$ is –

[ Directly not given in NCERT but NEET may ask] $S{O}_2\to$ Contain 3 atom
 $n=\frac{wt.}{M.wt.}=\frac{64}{64}$
Number of atoms present in 64 gm of $S{O}_2=\frac{64}{64}\times 3N_A$ 
$=36.02\times {10}^{23}$