The recommended dally allowance (RDA) of selenium in your diet is 55 micrograms. how many atoms of selenium is this? 4.19 x 10^17 atoms Se

4.2 × 10¹⁷ atoms of Se

Explanation:

Step 1: Convert the mass to grams

We will use the conversion factor 1 g = 10⁶ μg.

55 μg × 1 g/10⁶ μg = 5.5 × 10⁻⁵ g

Step 2: Calculate the moles corresponding to 5.5 × 10⁻⁵ g of Se

The molar mass of Se is 78.96 g/mol.

5.5 × 10⁻⁵ g × 1 mol/78.96 g = 7.0 × 10⁻⁷ mol

Step 3: Calculate the atoms in 7.0 × 10⁻⁷ moles of Se

We will use Avogadro's number: there are 6.02 × 10²³ atoms of Se in 1 mole of Se.

7.0 × 10⁻⁷ mol × 6.02 × 10²³ atom/1 mol = 4.2 × 10¹⁷ atom