1. 8

  2. 6

  3. 4

  4. 2

Answers (1)

This is a charge balancing question. 

Fe exists in two forms mainly Ferrous (Fe2+) and Ferric (Fe3+).

Let there are 100 oxygen atoms and x number of Fe3+ atoms and 96-x number of Fe2+ atoms.

Balance charge

x(+3)+(96-x)(+2) + 100(-2) = 0

\Rightarrow x = 8

The percentage of  Fe3+ ions is,    \frac{8}{96}\times 100 = 8.33\% \simeq 8\%

Option (1) is correct.

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