Question

The Molar mass of silicon is 28.09 grams/mole

Calculate the number of atoms in a 92.8 mg sample of silicon
Write your answer in scientific notation using three significant figures

Answer 1

1. Set up conversion factors.
92.8 mg x 1 g/10^3 mg x 1 mol/28.09 g x 6.022x10^23 atoms/1 mol

2. Cancel units.
1.99 x 10^21 Si atoms