How many atoms are contained in $5.6 \ L$ of oxygen gas at $STP$?

The number of moles of oxygen in $1 \ L$ of air containing $21 \%$ oxygen by volume,at standard temperature and pressure $(STP)$,is (in $mol$)

Natural abundances of $^{12}C$ and $^{13}C$ isotopes of carbon are $99\,\%$ and $1\,\%$,respectively. Assuming they only contribute to the molecular weight of $C_2F_4$,the percentage of $C_2F_4$ having a molecular mass of $101$ is $.....$

In how many grams of $CO_2$ is the number of $C$ atoms equal to $1.3699 \times 10^{23}$?

The mass of $1$ mole of electrons is

Which of the following contains the maximum number of molecules?