Question

what is the %fe in fe₂o₃?
20%
69.9%
35.0%
77.7%

Explanation:

Step1: Calculate molar mass of Fe₂O₃

The molar mass of Fe is approximately 55.85 g/mol and O is approximately 16 g/mol. For Fe₂O₃, molar mass $M = 2\times55.85+3\times16=111.7 + 48=159.7$ g/mol.

Step2: Calculate mass of Fe in Fe₂O₃

There are 2 Fe atoms in Fe₂O₃, so mass of Fe in Fe₂O₃ is $m_{Fe}=2\times55.85 = 111.7$ g/mol.

Step3: Calculate percentage of Fe

$\%Fe=\frac{m_{Fe}}{M}\times100=\frac{111.7}{159.7}\times100\approx69.9\%$

Answer:

69.9% (corresponding to the second option)