The number of atoms in $0.004 \ g$ of magnesium is:

Which of the following statements is incorrect?

Which gas among the following contains the maximum number of molecules at $STP$? (Molar masses in $g \ mol^{-1}$: $CO_{2}=44, Ar=39.9, CH_{4}=16, O_{2}=32$)

If $10^{21}$ molecules are removed from $200 \, mg$ of $CO_2$,then the number of moles of $CO_2$ left is .....

If $10^{21}$ molecules are removed from $200 \ mg$ of $CO_2$,then the number of moles of $CO_2$ left are .......... $\times 10^{-3}$.

Find the number of molecules present in $70 \text{ g}$ of dinitrogen $(N_2)$.