Calculate the number of moles present in 24 gm of oxygen gas.

(Atomic mass = $16$).

Q. Calculate the number of molecules present in $0.5$ moles of magnesium oxide $\left(MgO\right)$.

Q. Calculate the number of moles in
(i) $8g$ of oxygen atoms
(ii) $4.088\times {10}^{21}$ number of oxygen atoms (Atomic mass of $O=16u$)

Q. A gas cylinder contains $12\times {10}^{24}$ molecules of oxygen gas.
If Avogadro's number is $6\times {10}^{23}$; Calculate:
(i) the mass of oxygen present in the cylinder.
(ii) the volume of oxygen at S.T.P. present in the cylinder. $[O=16]$.

Q. Calculate the number of moles, molecules and total number of atoms present in $0.49$ g of helium gas.
[Given: $C=12,O=16,N=14,H=1,He=4$]

Q. If 16 g of oxygen contains 1 mole of oxygen atoms, calculate the mass of one atom of oxygen.