Final answer:
To calculate the number of vanadium atoms in a sample of vanadium(V) oxide (V2O5), convert the mass of the sample to moles using the molar mass of V2O5. Then, use Avogadro's number to find the number of vanadium atoms.
Step-by-step explanation:
To calculate the number of vanadium atoms in a 120.0 g sample of vanadium(V) oxide (V2O5), you need to first convert the mass of the sample to moles using the molar mass of V2O5. The molar mass of V2O5 is 181.88 g/mol. Therefore, there are 0.659 moles of V2O5 in the sample (120.0 g / 181.88 g/mol).
Next, use Avogadro's number (6.022 x 10^23) to convert the number of moles of V2O5 to the number of vanadium atoms. Since there is 1 vanadium atom in each formula unit of V2O5, there are 0.659 x 6.022 x 10^23 = 3.966 x 10^23 vanadium atoms in the sample.