Question

How do you determine the molar mass of helium?

Answer 1

Molar Mass:

1. It is defined as mass per mole for a compound.
2. The SI unit of molar mass $=\mathrm{Kg}{\mathrm{mol}}^{-1}$

Helium

1. It has the atomic number $2$ and is found in the upper right corner of the periodic chart. It is the most abundant noble gas in the family.
2. It has the same molar mass as its atomic mass since it exists in monoatomic form.
3. Since, the nucleus of helium is made of $2$ protons and $2$ neutrons.
4. Mass of $1$ proton $=1.007$and mass of $1$ the neutron$=1.008$. Therefore, the mass of $2$ proton$=2.007$ and mass of $2$ neutron$=2.008$.
5. The mass of helium atom $=$mass of $2$ proton$+$mass of $2$ neutron$=$$2.007+2.008\Rightarrow 4.015\mathrm{g}$.

Therefore, the molar mass of helium is $4.015{\mathrm{gmol}}^{-1}$.