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

$2.8 \times 10^{-3} \ mol$ 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 $mg$)

Find the number of molecules,number of carbon atoms,number of hydrogen atoms,and total number of atoms in $5.6 \ L$ of $CH_4$ at $STP$.

How many moles of water are present in $180 \ g$ of water?

$19.7 \ kg$ of gold was recovered from a smuggler. How many atoms of gold were recovered? (Atomic mass of $Au = 197 \ g/mol$)

Identify the number of moles of $H$ atoms present in $n$ moles of the organic compound represented as: (in $n$)