Calculate the number of :

(i) molecules [S = 32]

(ii) atoms in 192 g. of sulphur. [S₈]

(i) 1 mole of any substance contains 6.023 x 10²³ number of molecules.

S₈ = 8 atoms = 8 x 32 = 256.

256 g = 6.023 x 10²³ number of molecules

So, 192 g will have

$= \dfrac{6.023 \times 10^{23}}{256} \times 192 \\[0.5em] = \dfrac{192}{256} \times 6.023 \times 10^{23} \\[0.5em] = 0.75 \times 6.023 \times 10^{23} \text { molecules} \\[0.5em]$

(ii) Gram atomic mass of S = 32 g

32 g of S has 6.023 x 10²³ number of atoms

Therefore, 192 g will have

$= \dfrac{6.023 \times 10^{23}}{32} \times 192 \\[0.5em] = \dfrac{192}{32} \times 6.023 \times 10^{23} \\[0.5em] = 6 \times 6.023 \times 10^{23} \text { atoms} \\[0.5em]$