Give one example of homogeneous mixture.

Give one example of heterogeneous mixture.

Give one example of element.

Calculate number of moles of hydrogen in $0.448$ litre of hydrogen gas at STP.

The mass of an atom of hydrogen is $1.008 \mathrm{u}$. What is the mass of $18$ atoms of hydrogen.

Calculate the number of atom in the following (Given: Atomic mass of $\mathrm{I}=127 \mathrm{u}$).
$254 \mathrm{u}$ of iodine $\left(\mathrm{I}\right)$

Calculate the number of atom in $254 \mathrm{g}$ of iodine $\left(\mathrm{I}\right)$. (Given : Atomic mass of $\mathrm{I}=127 \mathrm{u}$)