Answer 1

254 g of iodine (I)
Atomic mass of iodine = 127 u
∴ Molar mass of iodine = 127 g mol^–1
Now,
Number of moles = `"Mass of a substance"/"Molar mass of a substance"`
= `(254  "g")/(127  "g"  "mol"^-1)`
= 2 mol
Now,
Number of atoms = Number of moles × Avogadro's constant
= 2 mol × 6.022 × 10²³ atoms/mol
= 12.044 × 10²³ atoms
= 1.2044 × 10²⁴ atoms
Number of iodine atoms in 254 g= 1.2044 × 10²⁴ atoms