Question

The total score for the correct statement(s) from the following is:
Given-
$Mn{O}_4^{\ominus }+8H^{\oplus }+5e^{-}\to M{n}^{2+}+4H_{2}O$; $E^{\oplus }=1.51V$
$F{e}^{3+}+e^{-}\to F{e}^{2+}$; $E^{\ominus }=0.77V$
$C{l}_2+2e^{-}\to 2C{l}^{\ominus }$; $E^{\ominus }=1.36V$
$C{e}^{4+}+e^{-}\to C{e}^{3+}$; $E^{\ominus }=1.76V$

	Statement	Score
a.	$Mn{O}_4^{\ominus }$ is a sufficiently strong oxidant in acidic solution (pH = 0) to oxidize $F{e}^{2+}$ ion.	1
b.	$F{e}^{2+}$ ion cannot be titrated against standard $KMn{O}_4$ solution if the medium is made acidic (pH=0) by adding HCl.	2
c.	$Mn{O}_4^{\ominus }$ ion cannot oxidize $C{e}^{3+}$ in acidic medium 9pH = 0).	3
d.	$F{e}^{2+}$ cannot be titrated against standard $KMn{O}_4$ solution in acidic medium (pH = 0) in the presence of $C{e}^{3+}$ ion.	4

Answer 1

Statement (a), (b) and (c) are correct.
Hence, total score = 1 + 2 + 3 =6
Statement (a) : pH = 0, means $\left[H^{\oplus }\right]$ = 1 M
$E_{red}^{\circ }$ of $Mn{O}_4^{\ominus }|M{n}^{2+}>E_{red}^{\ominus }$ of $F{e}^{3+}|F{e}^{2+}$
So $Mn{O}_4^{\ominus }$ will undergo reduction and acts s strong oxidant whereas $F{e}^{2+}$ undergoes oxidation. Statemnt (a) is correct.
Statement (b) : $Mn{O}_4^{\ominus }$ titrations in the presence of HCl are unstaisfactory since$C{l}^{\ominus }$ is oxidized to $C{l}^2$. Statement (b) is correct.
Statement (c) : Since $E_{redC{e}^{4+}|C{e}^{3+}}^{\ominus }>E_{redMn{O}_4^{\ominus }|M{n}^{2+}}^{\ominus }$. So $C{e}^{4+}$ will reduce to $C{e}^{3+}$. So $Mn{O}_4^{\ominus }$ cannot oxidize $C{e}^{3+}$ to $C{e}^{4+}$ Statement (c) is correct.
Statement (d) : $F{e}^{2+}$ can be titrated against $KMn{O}_4$ in acid medium $\left(\right[H^{\oplus }]=1M)$
Since $E_{redMn{O}_4^{\ominus }|M{n}^{2+}}^{\oplus }>E_{redF{e}^{3+}|F{e}^{2+}}^{\ominus }$
So $F{e}^{2+}$ can be oxidized to $F{e}^{3+}$ by $Mm{O}_4^{\ominus }$
But $C{e}^{3+}$ will not be oxidized to $C{e}^{4+}$
Since $E_{redC{e}^{4+}|c{e}^{3+}}^{\ominus }>E_{redMn{O}_4^{\ominus }|M{n}^{2+}}^{\ominus }$
So, statement (d) is wrong.