How much charge is required for the following reductions:(i) $1 mol$ of $Al ^{3+}$ to $Al$ ?(ii) $1 mol$ of $Cu ^{2+}$ to $Cu$ ?(iii) $1 mol$ of $MnO _{4}{ }^{-}$to $Mn ^{2+}$ ?

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How much charge is required for the following reductions:
(i) $1 mol$ of $Al ^{3+}$ to $Al$ ?
(ii) $1 mol$ of $Cu ^{2+}$ to $Cu$ ?
(iii) $1 mol$ of $MnO _{4}{ }^{-}$ to $Mn ^{2+}$ ?

How much charge is required for the following reductions:
(i) $1 mol$ of $Al ^{3+}$ to $Al$ ?
(ii) $1 mol$ of $Cu ^{2+}$ to $Cu$ ?
(iii) $1 mol$ of $MnO _{4}{ }^{-}$ to $Mn ^{2+}$ ?

Solution:

As we know that, 1 mole of electron has a charge of 1 faraday

(i) $A l^{3+}+3 e^{-} \rightarrow A l$
Required charge $=3 F$
$=3 \times 96487 C$
$=289461 C$
(ii) $C u^{2+}+2 e^{-} \rightarrow C u$
Required charge $=2 F$ $=2 \times 96487 C$ $=192974 C$
(iii) $MnO _{4}^{-} \rightarrow Mn ^{2+}$
i.e $Mn ^{7+}+5 e^{-} \rightarrow Mn ^{2+}$
Required charge $=5 F$
$=5 \times 96487 C$