Question

The mass of a single gold atom is 3.27×10-22 grams. How many gold atoms would there be in 43.2 milligrams of gold?

Answer 1

There are 1.32 × 10²⁰ atoms in 43.2 mg of gold.

Step 1. Convert grams of Au to moles of Au

Moles of SF₆ = 0.0432 g Au × (1 mol Au/196.97 g Au) = 2.193 × 10⁻⁴ mol Au

Step 2. Convert moles of Au to atoms of Au.

Atoms of Au = 2.193 × 10⁻⁴ mol Au × (6.022 × 10²³ atoms Au /1 mol Au)

= 1.32 × 10²⁰ atoms Au