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Assertion : Reduction potential of Mn $(+3$ to +2$)$ is more positive than Fe $(+3$ to +2$)$.
Reason : Ionisation potential of Mnis more than that of $\mathrm{Fe}$.
Options:
Reason : Ionisation potential of Mnis more than that of $\mathrm{Fe}$.
Solution:
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Verified Answer
The correct answer is:
If assertion is true but reason is false.
$\mathrm{Mn}^{2+}=[\mathrm{Ar}] 3 d^5$
$$
\begin{aligned}
& \mathrm{Mn}^{3+}=[\mathrm{Ar}] 3 d^4 \\
& \mathrm{Fe}^{3+}=[\mathrm{Ar}] 3 d^5
\end{aligned}
$$
$$
\mathrm{Fe}^{2+}=[\mathrm{Ar}] 3 d^6 \text {, }
$$
Thus, $\mathrm{Mn}^{2+}$ has more stable configuration than $\mathrm{Mn}^{3+}$ while $\mathrm{Fe}^{3+}$ has more stable configuration than $\mathrm{Fe}^{2+}$. Hence, reduction potential for $\mathrm{Mn}^{3+} / \mathrm{Mn}^{2+}$ couple is more positive than $\mathrm{Fe}^{3+} / \mathrm{Fe}^{2+}$.
$$
\begin{aligned}
& \mathrm{Mn}^{3+}=[\mathrm{Ar}] 3 d^4 \\
& \mathrm{Fe}^{3+}=[\mathrm{Ar}] 3 d^5
\end{aligned}
$$
$$
\mathrm{Fe}^{2+}=[\mathrm{Ar}] 3 d^6 \text {, }
$$
Thus, $\mathrm{Mn}^{2+}$ has more stable configuration than $\mathrm{Mn}^{3+}$ while $\mathrm{Fe}^{3+}$ has more stable configuration than $\mathrm{Fe}^{2+}$. Hence, reduction potential for $\mathrm{Mn}^{3+} / \mathrm{Mn}^{2+}$ couple is more positive than $\mathrm{Fe}^{3+} / \mathrm{Fe}^{2+}$.
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