Each point: 1.5 Marks
1. Atomic mass of Na = 23 u (Given)

Then, gram atomic mass of Na = 23 g

Now, 23 g of Na contains = 6.022 x 10²³ g number of atoms

Thus, 100 g of Na contains =   $6.022\times \frac{{10}^{23}}{23}\times 100$ number of atoms

= 2.6182 x 10²⁴ number of atoms.

2. Again, atomic mass of Fe = 56 u (Given)

Then, gram atomic mass of Fe = 56 g

Now, 56 g of Fe contains = 6.022 x 10²³ g number of atoms

Thus, 100 g of Fe contains = $6.022\times \frac{{10}^{23}}{56}\times 100$ number of atoms

= 1.0753 x 10²⁴ number of atoms.