A mole is not just no. of atoms or molecules in a substance.A mole can be defines as a chemical mass unit, defined to be 6.022 x 1023 molecules, atoms, or some other unit. The mass of a mole is the gram formula mass of a substance.
gram formula or atomic mass of CuO is 79.545 g/mol and that is of Ta2O5 is 441.893 g/mol, Cu=53.55g/mol and Ta=180.95g/mol
No. Of. Moles of a substance = Mass of that substance in grams/gram formula mass of that substance
I think you can do it further..... Good luck for your Xams....