Find the number of moles of sodium atoms in $6.9 \times 10^{-2} \ kg$ (Atomic mass $= 23 \ g \ mol^{-1}$)

Three $1 \ L$ flasks contain $N_2$,$Ne$,and $O_3$ gases respectively. At the same temperature and pressure,find the ratio of the total number of atoms present.

Calculate the number of moles present in $9.10 \times 10^{-2} \ kg$ of water.

Find the number of moles present in $0.448 \ L$ of dihydrogen at $STP$. (in $mol$)

$10 \ dm^3$ of $N_2$ gas and $10 \ dm^3$ of gas $X$ at the same temperature and pressure contain the same number of molecules. The gas $X$ is

How many moles of oxygen atoms are present in $64.4 \ g$ of $Na_2SO_4 \cdot 10H_2O$?