The number of moles of $BaCO_3$ which contain $1.5$ moles of oxygen atoms is:

What is the number of atoms present in $16 \ g$ of oxygen gas $(O_2)$?

Which has the maximum number of molecules among the following?

The number of sodium atoms in $2 \ mol$ of sodium ferrocyanide $Na_4[Fe(CN)_6]$ is .......... $\times 10^{23}$. (Given $N_A = 6.022 \times 10^{23} \ mol^{-1}$)

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