Worksheet - Moles and Atomic Mass 1 mole = 6.02 x 10 %) items of anything. 6.02 x 10 is also known as Avogadro's number. 1 mole of a pure substance = its formula mass or molecular mass expressed in grams. One mole of a pure substances - the molar mass of the pure substance. Molar mass units are g/mol. 1. How many Si atoms are in 0.783 mol of Si? 2. How many Na atoms are in 0.427 mol of Na? 3. How many N atoms are in 0.593 mol of N? 4. How many moles of Zn contain 6.07 x 10% atoms of Zn