We will determine the moles of each element first
moles = mass / atomic mass
Atomic weight of Al : 27 g/ mol
Atomic weight of P : 3 1g /mol
Atomic weight of O : 16 g /mol
Let the total mass of compound is 100g
The mass of each element will be
Al = 22.10 g
P = 25.40 g
O = 52.50 g
Moles of Al = mass / atomic mass = 22.10 / 27 = 0.819
Moles of P = mass / atomic mass = 25.40/ 31 = 0.819
Moles of O = mass / atomic mass = 52.50/ 16 = 3.28
Now we will divide the moles of each element with the lowest moles obtained to obtain a whole number ratio of moles of each element present
moles of Al = 0.819 / 0.819 = 1
moles of P = 0.819 / 0.819 = 1
moles of O = 3.28 / 0.819 = 4
So the empirical formula will be : AlPO4
