Question

In which of the following compounds, iron has an oxidation state of $+3$?

• A. $Fe(N{O}_3{)}_2$
• B. $Fe{C}_2{O}_4$
• C. $\left[Fe\right(H_{2}O{)}_6]C{l}_3$
• D. $(N{H}_4{)}_{2}S{O}_4\cdot FeS{O}_4\cdot 6H_{2}O$

Answer 1

The correct option is C $\left[Fe\right(H_{2}O{)}_6]C{l}_3$

Let $Fe$ has $x$ oxidation state

In $Fe{\left(N{O}_3\right)}_2$: $x-2(+1)=0,x=+2$

In $Fe{C}_2{O}_4$: $x-2=0,x=+2$

In $\left[Fe{\left(H_{2}O\right)}_6{Cl}_3\right]$: $x+6\left(0\right)+3(-1)=0,x=+3$

In $({NH}_4{)}_2{SO}_4.{FeSO}_4.6H_{2}O$: $x-2=0,x=+2$ (In $({NH}_4{)}_2{SO}_4.{FeSO}_4.6H_{2}O$ for calculation of oxidation state we would only consider ${FeSO}_4$)

So in option C iron has an oxidation state of +3.