Calculate the number of moles of magnesium present in a magnesium ribbon weighing $12 \, g$. The molar atomic mass of magnesium is $24 \, g \, mol^{-1}$. (in $, mol$)

Calculate the number of atoms in $0.02$ mole of carbon.

If bromine atom is available in the form of,say,two isotopes $_{35}^{79}Br$ $(49.7 \%)$ and $_{35}^{81}Br$ $(50.3 \%),$ calculate the average atomic mass of bromine atom. (in $,u$)

Mention the name given to the number of $6.022 \times 10^{23}$ particles.

$(i)$ $(a)$ What do you understand by $1 \text{ amu}$ or $1 \text{ u}$?
$(b)$ How is it linked with relative atomic mass?
$(ii)$ How do we know the presence of atoms if they do not exist independently for most of the elements?

Define the term mole.