Numbers of gram atoms of oxygen present in $0.8 \ mol$ of $C_4H_6O_6$ would be

What is the numerical value of $\frac{N}{n}$? (Where $N$ is the number of molecules in a given gas sample and $n$ is the number of moles of the gas.)

If $500 \ mL$ of $NH_3$ gas at $STP$ contains $6.0 \times 10^{21}$ molecules,how many molecules will $100 \ mL$ of $CO_2$ gas contain at $STP$?

$A$ thin layer of cobalt is deposited on a plate with a total area of $0.5 \ m^2$ and a thickness of $0.005 \ cm$. How many cobalt atoms are deposited on the plate? (Density of cobalt $= 8.9 \ g \ cm^{-3}$,Atomic mass of $Co = 59 \ g \ mol^{-1}$)

Which one of the following has the maximum number of atoms?

The number of atoms in $8 \ g$ of sodium is $x \times 10^{23}$. The value of $x$ is ...... (Nearest integer).
$[ \text{Given}: N_{A} = 6.02 \times 10^{23} \ mol^{-1}, \text{Atomic mass of } Na = 23.0 \ u ]$