How many atoms are in 125 g of iron?

Question

3.72 x 10-24 atoms Fe ?
1.347 x 1024 atoms Fe ?
2.69 x 1023 atoms Fe ?
4.20 x 1027 atoms Fe ?
1.35 x 1024 atoms Fe ?

Answer 1

[(125g) / (56g/mol)] x (6.022x 10^23) = 1.347 x 10^24

6.022 x 10^23 is avogadro's number
56g/mol is the atomic weight of iron

Answer 2

Iron Fe has a mass number (relative atomic weight) of 56.
This means that 56 g = 1 mole of iron
1 mole of any substance contains (6 x 10 ^23) particles (Avogadro's number)
Therefore 1 g of iron contains [1/56] x (6 x 10^23) Fe atoms
Hence 125 g of iron contains 125 x [1/56] x (6 x 1o^23) Fe atoms
this should work out to be the second choice 1.347 x 10^24 Fe atoms.

Note to students: In any Mole Concept calculations, try to use proportion method, instead of trying to remember and recall the confusing formuli your teachers throw at you. I have always taught my Chemistry students to use the proportion approach.
Show this working to your Chem teacher and see what he says.

Answer 3

the atomic weight of iron Fe is 56

125 g = 125/56 = 2.23 atom-gramme

1 atome-gram = 6.02*10^23 atoms iron

so 2.23 atom-gramme = 6.02*2.23 *10^23 =1.347 10^24 atoms Fe

Answer 4

(NOTE: YOU HAVE TO USE THE ATOMIC WEIGHT OF IRON, 55.85 g/mol. OTHERWISE YOU DO NOT GET 1.347x10^24 AS THE CORRECT ANSWER. INSTEAD YOU HAVE 1.344x10^24.)

The atomic weight of iron (Fe) is 55.85 (g/mol), so 125 g of iron is 125/55.85=2.238 (mol), which is
2.238x6.02x10^23
=1.347x10^24 (atoms of Fe)

Answer 5

525 600 minutes.