Converting Moles to Number of Atoms Calculate the number of H atoms in 0.350 mol of C6H12O6. How many sulfur atoms are in (a) 0.45 mol BaSO4 and (b) 1.10 mol of aluminum sulfide?
Answer: Step 1 We are given the amount of a substance (0.350 mol) and its chemical formula C6H12O6. The unknown is the number of H atoms in the sample. Avogadro’s number provides the conversion factor between number of moles of C6H12O6 and number of molecules of C6H12O6: 1 mol C6H12O6 = 6.02 * 10^23 molecules of C6H12O6. Once we know the number of molecules of C6H12O6, we can use the chemical formula, which tells us that each molecule of C6H12O6 contains 12 H atoms. Thus, we convert moles of C6H12O6 to molecules of C6H12O6 and then determine the number of atoms of H from the number of molecules of C6H12O6: Moles C6H12O6 molecules C6H12O6 atoms H. H atoms =(0.350 mol C6H12O6)(6.023*10 molecules of C6H12O6)/1 mole of C6H12O6)*(12 H atoms )/(1 molecule of C6H12O6). =2.53*10 H atoms . Step 2 One mole of any matter is equal to 6.023*10 number of particles in the mater. 23 For example, 1 mole of carbon atoms means there are 6.023*10 number of atoms of carbon. (a) Chemical formula of barium sulphate is BaSO4. 1 molecule of BaSO4 contains 1 atom of S. So ,calculate the number of atoms of S in 0.45 mol of BaSO4 as follows: (number of atoms of S in 0.45 mol of BaSO4)=(0.45)(number of atoms of S in one molecule 23 of BaSO4)(6.023*10 ). =(0.45)(1)(6.023*10^23). 23 =2.71*10 atoms. Therefore ,the number of sulfur atoms in 0.45 mol of BaSO4 is 2.7*10 atoms.23