One atom of an element weighs $3.32 \times 10^{-23} \ g$. How many gram atoms are there in $20 \ kg$ of the element?

The number of oxygen atoms in $0.2 \ mol$ of sodium carbonate decahydrate is :-

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 $.....$

If one atom of an element $X$ weighs $6.643 \times 10^{-23} \ g$,then find the number of moles of atoms in $50 \ kg$ of element $X$. (in $moles$)

Explain the terms: Avogadro constant,molar volume of $1$ mole of gas,and $STP$.

The number of neutrons in $5 \ g$ of $D_2O$ ($D$ is $_1^2H$) are ................ $N_A$.