The mass of $1$ mole of electrons is

$80 \ g$ of oxygen contains as many atoms as in

$2.8 \times 10^{-3} \ mol$ of $CO_2$ is left after removing $10^{21}$ molecules from its '$x$' $mg$ sample. The mass of $CO_2$ taken initially is. Given: $N_A = 6.02 \times 10^{23} \ mol^{-1}$. (in $mg$)

The mass of $1$ mole of electrons is .......

Consider two sealed jars of equal volume. One contains $2 \ g$ of hydrogen at $200 \ K$ and the other contains $28 \ g$ of nitrogen at $400 \ K$. The gases in the two jars will have

$10 \ g$ each of $CO_2$,$NH_3$,and $O_2$ were taken in three separate flasks. What is the correct decreasing order of the number of atoms?