Mole-atom conversions 1. how many moles are 1.55 x 1027 atoms of zinc (zn)? 2. how many atoms are in 25.0 moles of calcium (ca)? 3. how many atoms are in 0.35 moles of carbon (c)? 4. how many moles are 7.6 x 1024 atoms of helium? mole-mass conversions how many moles in 28.o grams of oxygen? what is the mass of 5.0 moles of iron? find the number of moles of argon in 452 g of argon. find the grams in 16.5 mol of hydrogen.