How many total atoms are in 0.560 g of P₂O₅?

Answer 1

molar mass P2O5 2*31 + 5*16 = estd 142
mols P2O5 in 0.560 g = g/molar mass = estd 0.004
So you have 2*0.004 = about 0.008 mols P
and 5 x 0.004 = about 0.02 mols O
Total mols = aout 0.008 + 0.2 = about 0.28
Now you know that 1 mol of anything has 6.02E23 anythings in it.
Remember all of these are estimates so you nee to redo all the calculations.
Post your work if you get stuck.