There are eight moles of oxygen atoms in each mole of "Fe"_3("PO"_4)_2"Fe3(PO4)2. To answer this question, you must convert the given mass of "Fe"_3("PO"_4)_2"Fe3(PO4)2 to moles of "Fe"_3("PO"_4)_2"Fe3(PO4)2. Then multiply the moles of "Fe"_3("PO"_4)_2"Fe3(PO4)2 times (8"mol O)/(1 mol Fe"_3("PO"_4)_2")(8mol O)/(1 mol Fe3(PO4)2) to determine the number of moles of oxygen. Then multiply the moles of oxygen times 6.022xx"10"^236.022×1023 "atoms O"atoms O.
Given/Known:
mass "Fe"_3("PO"_4)_2"Fe3(PO4)2=="120.23 g"120.23 g
molar mass "Fe"_3("PO"_4)_2"Fe3(PO4)2 = ="357.478g/mol"357.478g/mol
1 mole "Fe"_3("PO"_4)_2"Fe3(PO4)2 contains 8 moles oxygen atoms
1 mole O atoms = 6.022xx"10"^236.022×1023 "atoms"atoms
Unknown:
number of oxygen atoms in "120.23g Fe"_3("PO"_4)_2120.23g Fe3(PO4)2
Solution:
1. Convert given mass of "Fe"_3("PO"_4)_2"Fe3(PO4)2 to moles.
120.23color(red)cancel(color(black)("g Fe"_3("PO"_4)_2))xx(1 "mol Fe"_3("PO"_4)_2)/(357.478color(red)cancel(color(black)("g Fe"_3("PO"_4)_2)))= "0.336328 mol Fe"_3("PO"_4)_2"
2. Convert moles "Fe"_3("PO"_4)_2" to moles O.
0.336328color(red)cancel(color(black)("mol Fe"_3("PO"_4)_2))xx(8"mol O")/(1color(red)cancel(color(black)("mol Fe"_3("PO"_4)_2)))="2.690624 mol O"
3. Convert moles O to atoms O.
2.690624color(red)cancel(color(black)("mol O"))xx(6.022xx10^23"atoms O")/(1color(red)cancel(color(black)("mol O")))=1.6203xx10^24"atoms O" (answer rounded to five significant figures)
