What is the number of moles of water molecules present in a mole of carnallite?

If $3.01 \times 10^{20}$ molecules are removed from $98 \ mg$ of $H_2SO_4$,how many moles of $H_2SO_4$ are removed?

Assertion $(A)$: Equal moles of different substances contain the same number of constituent particles.
Reason $(R)$: Equal weights of different substances contain the same number of constituent particles.
The correct answer is

The number of molecules in $8.96 \ L$ of a gas at $0^{\circ}C$ and $1 \ atm$ pressure is approximately

Calculate the number of valence electrons in $4.2 \ g$ of $N_3^-$ ions in terms of $N_A$ ($N_A$ = Avogadro constant). (in $N_A$)

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