What is the number of molecules of $SO_2$ present in $64 \ g$ of $SO_2$?

The mass of $4.48 \ dm^3$ of a certain gas is $5.6 \ g$ at $STP$. Assuming ideal behaviour,identify the probable gas from the following.

The volume of a gas in a discharge tube at $STP$ is $1.12 \times 10^{-7} \ mL$. What is the number of molecules of the gas in the tube?

What is the value of Avogadro's number?

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 $O$

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