Estimate the number of atoms in 7.827 g of iron using the mass of an atomic mass unit (1.661 x 10^-27). The atomic mass of Fe is 55.85 u.

Answer 1

You are ignoring units.

mass of iron is in grams.
atomic mass is in grams.
amu is in kg.
So you have an incompatability in units.

number atoms= massiron/(massofeach atom)

where mass ofeach atom=55.85u*mass/u

so fix the units to be compatable, and you have it.

Answer 2

that is my problem i am not sure how to fix the units. Do I divide the grams by 1000 so i would have 0.007927 grams then multiply by 55.85? Thank you so much for any help.

Answer 3

1*10^23 atoms