How much charge is required for the following reductions:

Question:

How much charge is required for the following reductions:

(i) 1 mol of Al3+ to Al.

(ii) 1 mol of Cu2+ to Cu.

(iii) $1 \mathrm{~mol}$ of $\mathrm{MnO}_{4}^{-}$to $\mathrm{Mn}^{2+}$.

Solution:

(i) $\mathrm{Al}^{3+}+3 \mathrm{e}^{-} \longrightarrow \mathrm{Al}$

$\therefore$ Required charge $=3 \mathrm{~F}$

= 3 × 96487 C

= 289461 C

(ii) $\mathrm{Cu}^{2+}+2 \mathrm{e}^{-} \longrightarrow \mathrm{Cu}$

$\therefore$ Required charge $=2 \mathrm{~F}$

= 2 × 96487 C

= 192974 C

(iii) $\mathrm{MnO}_{4}^{-} \longrightarrow \mathrm{Mn}^{2+}$

i.e., $\mathrm{Mn}^{7+}+5 \mathrm{e}^{-} \longrightarrow \mathrm{Mn}^{2+}$

$\therefore$ Required charge $=5 \mathrm{~F}$

= 5 × 96487 C

= 482435 C

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