Calculate the number of atoms present in :

(a) 10 g of Chlorine

(b) 10 g of Nitrogen

(a) Mass of 1 mole of chlorine (Cl) is 35.5 g

35.5 g of chlorine (Cl) contains 6.022 × 10²³ atoms

∴ 10g of chlorine (Cl) contains = $\dfrac{6.022 \times 10^{23} \times 10}{35.5}$

= 1.7 x 10²³ atoms

(b) Mass of 1 mole of nitrogen (N) is 14 g

14 g of nitrogen (N) contains 6.022 × 10²³ atoms

∴ 10g of nitrogen (N) contains = $\dfrac{6.022 \times 10^{23} \times 10}{14}$

= 4.3 x 10²³ atoms