Phosphorus pentoxide, P2O5, containing a total of 4.91x10^22 atoms of phosphorus and oxygen. what is the amount in moles of molecules? ?

Question

A sample of diphosphorus pentoxide, P2O5(s), containing a total of 4.91 × 10^22 atoms of phosphorus and oxygen. Calculate the amount in moles of molecules?  

Answer 1

Each molecule of P2O5 has 2 atoms of P and 5 atoms of O for a total of 7 atoms per molecule.  Converting 4.91x10^22 atoms into molecules, we have...

4.91x10^22 atoms x 1 molecule / 7 atoms = 7x10^21 molecules.  

To convert this to moles, we use 6.02x10^23 molecules / mole and so...

7x10^21 molecules x 1 mol / 6.02x10^23 molecules = 1.2x10^-2 moles = 0.012 mol