Which of the following weighs most?

(i)$0.1$ mole of sodium (ii)${10}^{23}$ molecules of ${\mathrm{SO}}_2$

(iii) $0.1\mathrm{g}$ atom of iron (iv) ${10}^{23}$ atoms of silver

(Atomic masses $\mathrm{Na}=23.0\mathrm{u}, \mathrm{S}=32.0\mathrm{u}, 0=16.0\mathrm{u}, \mathrm{Fe}=56.0\mathrm{u}, \mathrm{Ag}=108.0\mathrm{u}$)

If $1\mathrm{g}$ of sulphur dioxide contains $\mathrm{X}$ molecules, what will be the number of molecules in $1\mathrm{g}$ of methane?

(Atomic masses $\mathrm{S}=32.0\mathrm{u}, \mathrm{O}=16.0\mathrm{u}, \mathrm{C}=12.0\mathrm{u}, \mathrm{H}=1.0\mathrm{u}$)

Calculate the number of moles and molecules in $4 \mathrm{g}$ of oxygen.

Calculate the number of moles and molecules in $11 \mathrm{g}$ of carbon dioxide.

The mass of one molecule of a substance is $11.79\times {10}^{-26} \mathrm{kg}$. Calculate its molar mass? What could this substance be?

The mass of one atom of an element $\mathrm{X}$ is $2.0\times {10}^{-23} \mathrm{g}$. Calculate the atomic mass of element $\mathrm{X}$.

The mass of one atom of an element $\mathrm{X}$ is $2.0\times {10}^{-23} \mathrm{g}$. What could element $\mathrm{X}$ be?