Explanations:

First, convert the number of moles of sulfuric acid to the number of molecules. 2.1 mol H2SO4 * (6.022 * 10^23 molecules / mol) = 1.265 * 10^24 molecules H2SO4. Each molecule of sulfuric acid is made up of 7 atoms: 2 hydrogen atoms, 1 sulfur atom, and 4 oxygen atoms. Therefore, the total number of atoms in 2.1 mol of sulfuric acid is 7 atoms / molecule * 1.265 * 10^24 molecules = 7.56 * 10^24 atoms.