Question: how many atoms are present in 2 moles of calcium?
Answer: It is equal to Avogadro's number (NA), namely 6.022 x10^23. A mole of a compound will have 6.02 x 10^23 molecules, so the number of atoms in a mole is 6.02 x 10^23 x number of atoms in a molecule. One Molecule of Ca(OH)2 has 5 atoms. Therefore, one mole of Ca(OH)2 has 6.022 x10^23 x 5 = 30.11 x 10^23 atoms.