Question

The standard redox potentials E${}^o$ of the following systems are:

	System	E${}^o$ (volts)
(i)	$Mn{O}_4^{-}+8H^{+}+5e^{-}\to M{n}^{2+}+4H_{2}O$	1.51
(ii)	$S{n}^{2+}\to S{n}^{4+}+2e^{-}$	0.15
(iii)	$C{r}_2{O}_7^{2-}+14H^{+}+6e^{-}\to 2C{r}^{3+}+7H_{2}O$	1.33
(iv)	$C{e}^{3+}\to C{e}^{4+}+e^{-}$	1.61

The oxidising power of the various species are related as:

• A. $C{r}_2{O}_7^{2-}>Mn{O}_4^{-}$
• B. $C{e}^{4+}>S{n}^{4+}$
• C. $E{c}^{4+}>Mn{O}_4^{-}$
• D. $Mn{O}_4^{-}>S{n}^{4+}$

Answer 1

Answer: (B), (C), (D)

The correct options are
B $C{e}^{4+}>S{n}^{4+}$
C $E{c}^{4+}>Mn{O}_4^{-}$
D $Mn{O}_4^{-}>S{n}^{4+}$

Species with higher reduction potential have higher oxidising power.
$S.R.P\uparrow O.A\uparrow$ $S.R.P=-S.O.P$
$E_{c{e}^{+4}|C{e}^{+3}}^o>E_{Mn{O}_4^{-}|M{n}^{+2}}^o>E_{C{r}_2{O}_7^{-2}|C{r}^{+3}}^o>E_{S{n}^{+4}|S{n}^{+2}}^o$
1.61 1.51 1.33 0.15