The number of moles of a gas in $1 \, m^3$ of volume at $NTP$ is

In $3$ moles of ethane $(C_{2}H_{6})$,calculate the following:
$i.$ Number of moles of carbon atoms.
$ii.$ Number of moles of hydrogen atoms.
$iii.$ Number of molecules of ethane.

Arrange the following in order of increasing mass:
$I$. $1$ mole of $N_2$
$II$. $0.5$ mole of $O_3$
$III$. $3.011 \times 10^{23}$ molecules of $O_2$
$IV$. $0.5$ gram atom of $O$

If $24 \times 10^{23}$ molecules are removed from $50 \ g$ of hydrogen gas $(H_2)$,how many moles of hydrogen remain?

The number of hydrogen atoms present in $5.4 \ g$ of urea is : (Given : Molar mass of urea: $60 \ g \ mol^{-1}$, $N_{A} = 6.022 \times 10^{23} \ particles \ mol^{-1}$)

Calculate the mass of oxygen present in $0.1 \ mol$ of $Na_2CO_3 \cdot 10H_2O$. (in $g$)