The number of moles in $620 \ g$ of sodium oxide is ..... moles.

The largest number of molecules is in

The number of molecules and atoms present in $1.2 \ g$ of ozone $(O_3)$ are respectively:

The mass of $1$ mole of electrons is

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 mass of hydrogen (in grams) present in $1.0 \text{ L}$ of pure water of density $1.0 \text{ g cm}^{-3}$ is