The standard electrode potential (in V) values for $\mathrm{Al}^{3+}$ / $\mathrm{Al}, \mathrm{Tl}^{3+} /…
The standard electrode potential (in V) values for $\mathrm{Al}^{3+}$ / $\mathrm{Al}, \mathrm{Tl}^{3+} / \mathrm{T} 1$ are respectively
$-1.66,-1.26$
$+1.66,+1.26$
$-1.66,+1.26$
$+1.66,-1.26$
Solution
($\mathrm{Al}^{3+}$ is much more stable than $\mathrm{Al}$ and due to electropositive nature, the standard reduction potential of $\mathrm{Al}^{3+} / \mathrm{Al}$ is negative.
$\mathrm{Tl}$ is not as electropositive as $\mathrm{Al}$ and therefore $\mathrm{Tl}^{3+}$ can easily be reduced to Tl because of which its SEP value is positive.