Calculate the number of atoms in

(i) 8 g of 02 molecules.

(ii) 0.1 mole of C-atoms.

[Atomic mass of O = 16, = 6.022 x ${10}^{23}$ mol-1]

(i) 1 mole of ${{O}*{2}}$ = 32 g = 6.022 x ${10}^{23}$
32 g of ${{O}*{2}}$ contains 6.022 x ${10}^{23}$ molecules.

8 g of ${{O}_{2}}$ contain = 6.022 x ${10}^{23}$ x 8 / 32 = 1.505 x ${10}^{23}$ atoms.

(ii) 1 mole of carbon atoms contains 6.022 x ${10}^{23}$ atoms.

0.1 mole of C- atoms will contain = 6.022 x ${10}^{23}$ x 0.1 / 1 =6.022 x ${10}^{22}$ atoms.