Question

Match the column I with column II and mark the appropriate choice.

	Column I ( Compound )		Coloumn II (Oxidation state of $Fe$)
( A )	$K_3\left[\right(Fe\left(OH{)}_6\right]$	(i)	+8/3
( B )	$K_2\left[Fe{O}_4\right]$	(ii)	+2
( C )	$FeS{O}_4,(N{H}_4{)}_{2}S{O}_{4}6H_{2}O$	(iii)	+3
( D)	$F{e}_{3}O4$	(iv)	+6

• A. $\left(A\right)\to \left(iii\right),\left(B\right)\to \left(i\right),\left(C\right)\to \left(ii\right),\left(D\right)\to \left(iv\right)$
• B. $\left(A\right)\to \left(iii\right),\left(B\right)\to \left(iv\right),\left(C\right)\to \left(ii\right),\left(D\right)\to \left(i\right)$
• C. $\left(A\right)\to \left(i\right),\left(B\right)\to \left(iii\right),\left(C\right)\to \left(ii\right),\left(D\right)\to \left(iv\right)$
• D. $\left(A\right)\to \left(iv\right),\left(B\right)\to \left(ii\right),\left(C\right)\to \left(i\right),\left(D\right)\to \left(iii\right)$

Answer 1

The correct option is B $\left(A\right)\to \left(iii\right),\left(B\right)\to \left(iv\right),\left(C\right)\to \left(ii\right),\left(D\right)\to \left(i\right)$

Let the oxidation number of $Fe$ be $x$.

Oxidation number of the ligands are: $H=K=+1$, $O=-2,OH=-2+1=-1,N{H}_4=+1,S{O}_4=-2,H_{2}O=0$

$\left(A\right)$ $K_3\left[Fe\right(OH{)}_6]$: $3\times 1+x+6\times (-1)=0$

$x+3-6=0$ or $x=+3$ =(iii)

$\left(B\right)$ $K_2\left[Fe{O}_4\right]$: $2\times 1+x+4\times (-2)=0$

$x+2-8=0$ or $x=+6$=(iv)

$\left(C\right)$ $FeS{O}_4.(N{H}_4{)}_{2}S{O}_4.6H_{2}O$: $x+(-2)+2\times 1+(-2)+6\times 0=0$=(ii)

$x-2+2-2+0=0$ or $x=+2$

$\left(D\right)$ $F{e}_3{O}_4$: $3\times x+4\times (-2)=0$

$3x-8=0$ or $x=+8/3$ $=(i)$

$\left(A\right)-\left(iii\right),\left(B\right)-\left(iv\right),\left(C\right)-\left(ii\right),\left(D\right)-\left(i\right)$